Low millivolts from a thermopile

DIY: Gas Fireplace Won’t Light? How to Clean your Thermopile and Thermocouple 286

Gas Fireplace Won't Light?


As with all my DIY posts, anything you decide to do as a result of reading this post, you do so at your own risk. With gas and flames involved, things can get dangerous — as in blow-your-house-up dangerous. So hire an expert if you’re not comfortable doing any of this in a safe manner.

My Gas Fireplace Won’t Light

If your gas fireplace isn’t starting, there could any number of possible issues contributing. First, check to see if your pilot light is lit. If it’s not, maybe it just blew out. Try to reignite the pilot it by following the fireplace manufacturer’s instructions.

Diagnosing a Thermocouple Problem

If your pilot light ignites but won’t stay lit, then the problem is most likely related to your thermocouple,  a metal sensor (about the size and shape of a sharpened pencil) that heats up by direct contact with the pilot light’s flame, telling your gas valve that the pilot light is lit so it’s safe to open the valve to let gas flow.

Diagnosing a Thermopile Problem

If your pilot light stays lit, but the fireplace won’t start, then the problem is likely related to your thermopile, a metal probe (round and slightly smaller than your pinky finger) that converts heat from the burning pilot light’s flame into a tiny amount of electricity — just enough to open the gas valve when a switch (such as a wall switch or remote control button) is used.

Don’t Replace Your Thermopile or Thermocouple Right Away

Because your thermopile and thermocouple are both designed to be engulfed by your pilot light’s flame at all times, it’s natural that carbon deposits from that burn will build up over time, limiting their effectiveness. Both probes are relatively easy and cheap to replace, but it’s much faster and cheaper to try cleaning them first.

Recently, I noticed that it was taking a long time for my gas fireplace to light. The pilot light would stay lit just fine, but when I’d hit the wall switch, I’d wait 5-6 seconds and the fireplace would light with a dramatic “WHOOOOMPH!” Or, sometimes, the fireplace wouldn’t light at all.

How to Check your Thermopile Output with the TH/TP Contacts

Because I knew my thermocouple was working fine (since the pilot light would stay lit), I decided to check the output of the thermopile to see how much electricity it was generating. If it’s making just barely enough, the gas valve will open, but slowly, creating the gas build-up and the WHOOOMPH! But if it’s making nowhere near enough, the gas valve won’t open at all, and the fireplace won’t light.

If you open the access panel on your gas fireplace (usually on the bottom), you’ll see the fireplace’s gas plumbing, the gas valve itself, and a bunch of wires. On the valve, you’ll normally see some electrical contacts labelled TH and TP.

TH/TP Gas Fireplace Contacts

TH/TP Gas Fireplace Contacts

The TH stands for “THermostat,” and those two wires connect to the thermostat device (or in most cases, a wall switch) that tells the valve to open. Under normal conditions, with the pilot light lit, closing the circuit between the two TH contacts will open the gas valve and ignite your fireplace’s main burner.

The TP stands for “ThermoPile,” and (not surprisingly) those two wires connect to the thermopile to feed the small amount of electricity created to the gas valve so it can open when the TH contacts are switched “closed.” To test the electrical output of the thermopile, make sure the pilot light is light and connect a multimeter to both TP connectors. Set your multimeter to its lowest direct current (DC) setting, then touch the multimeter’s red probe to the bottom TP terminal (it will usually share the terminal with a TH connector) and the black probe the TP terminal up top. If you’re having trouble telling which connectors go where, just follow the wires. If they head out to the wall switch, or to a remote control receiver box, they’re the TH wires. If they head underneath and up toward the pilot light assembly, those are the TP wires.

Low millivolts from a thermopile

Low millivolts from a thermopile

As you can see from the picture above, my thermopile was putting out .358 volts, or 358 millivolts. Most thermopiles are designed to generate between 500-750 millivolts from the heat of a normal pilot light, so mine was well on the low side. And although the owner’s manual on my gas valve swears it will operate with as low as 300 millivolts, that simply wasn’t the case.

Cleaning the Thermopile

I’ve replaced thermopiles in the past, and although it wasn’t very difficult, I figured I’d try the easy route first. I turned the round knob on the gas valve to the OFF position (which killed the pilot light) and then closed the shutoff valve on the hose that fed gas to the unit (VERY important). I removed the screen and glass cover from the fireplace, and then took a look at the pilot burner assembly.

Gas Fireplace Pilot Assembly

Gas Fireplace Pilot Assembly. From left to right: thermopile, pilot nozzle, pilot ignitor, and thermocouple.

As you can see from the above photo, there’s a fair amount of white crud built up on both the thermopile (far left) and the thermocouple (far right). You can also see from the shape of the pilot nozzle that it directs the flame of the pilot light into three directions: left to heat the thermopile, right to heat the thermocouple, and straight ahead to ignite the full burner when the gas valve opens.

I used a combination of a cheap stainless steel brush, some 000 extra-fine steel wool, and some fine grit sandpaper to remove as much baked-on soot as possible from the thermopile, and I figured I may as well clean the thermocouple while I was there. This gives them both more clean surface area to do their respective jobs. I spent around 5-10 minutes trying to maneuver around the tight spaces and get things as clean as I could.

Re-Testing the Cleaned Thermopile

When everything was clean, I turned on the valve on the hose, then followed my fireplace manufacturer’s instructions for re-igniting the pilot light, which for my unit is simply depressing and turning the round knob on the gas valve to PILOT and then clicking the ignitor button until the pilot lights. I let the pilot heat the thermopile for a few minutes, and then a took another reading:

Better Voltage from the Thermopile

Better Voltage from the Thermopile

The output of 478 millivolts shown above was way better than the 358 I started with, and after a couple of minutes I actually saw it climb to 530 millivolts. I replaced the fireplace glass (which I’d also cleaned with glass cleaner while it was off), put the screen back on, then hit the wall switch to test. The fireplace ignited immediately! I hit the switch a few more times to make sure, and it lit every time. And while the electrical output of the cleaned thermopile was still on the lower side, it’s again enough power to reliably open the gas valve, and hopefully this cleaning bought me at least another few years with the existing thermopile and thermocouple. However, when it does eventually become time to replace either of them, just go ahead replace both. The parts are cheap — the real bother is removing the logs and pushing/pulling the new probes out of and back in to the rubber grommets (or what’s left of them if they’ve melted) underneath the burner assembly.

Cleaning Steps Video

This fireplace isn’t exactly the same as the one I used to write this article, but the main principles are the same. Once of my readers shared this video with me, and it does a good job of quickly showing the steps involved in cleaning your thermocouple.

Replacing a Thermocouple or Thermopile if Cleaning Didn’t Work

If cleaning the thermocouple didn’t allow your pilot light to stay lit, or cleaning the thermopile didn’t allow the pilot light to generate enough electricity to open your gas valve and ignite the burner, it might be time to replace one of them. However, the hardest part of the job is actually taking the logs apart and gaining access to where the thermocouple and thermopile connect to the gas valve, so if you’re going to replace one, just go ahead and replace them both at the same time. You can take out the old ones, take them to any local hardware store, and pick up a generic replacement. Gas water  heaters generally use the same ones as gas fireplaces.

Final Thoughts

Again, please don’t attempt any of this unless you’re certain you can do it in a safe manner. Hire a gas fireplace expert if you have any doubts. But if you’re handy, testing and cleaning your thermopile and thermocouple can extend their service life, save you some money, and make your living room warm again.

UPDATE – Please Read!

I appreciate all the positive comments on this post. It’s one of the most popular articles on my blog! And if you’re here, that means you have a gas burning fireplace. And if you have a gas burning fireplace, that means it’s generating carbon monoxide. And that means you need to read another blog post I wrote. Please. If you feel this article has saved you time or money, you can pay me back by reading my blog post on carbon monoxide poisoning and taking the proper precautions. Thank you!

I welcome your feedback in the comments below!

  • Mike Craft

    My only comment is that you have a really cool blog, all kinds of good stuff!!! Nice work on the DIY!

    • Thanks, Mike. Only a few decades ago, even men who worked as professionals, and wore ties to work, knew how to fix their own car if it broke down on the way home from work, repair the furnace if it stopped working, build their own addition on to their house, handle a firearm, get philosophical, cook a steak on the BBQ, throw a punch, quote a Bible verse, hit a baseball, give fatherly advice, and score a bowling game. My dad was that type of guy, and there’s a real shortage of those types of guys these days. In a world of overspecialization, we’re losing the “well rounded guy.” So my blog purposely wanders around a variety of topics. Yes, I’m a professional geek, but first and foremost, I’m a guy. And guys should be into all sorts of awesome things! 🙂

      • Bennett

        Hi Steve. Great post. So nice to see someone giving useful information, instead of all those pro sites that just say this is dangerous and you should call someone. I like to do all the work on my motorcycles, car, house, so that doesn’t fly with me.

        Anyway, I moved into an apartment with no joy in the fireplace. Didn’t seem there was any gas coming, so called the gas company to check it and their guy said it probably needed either cleaning or thermocouple replaced. So I bought one and put it in, and now I get strong, nice blue flame from the pilot, and a reading of 500 mw as it heats up. But (and you knew there had to be a but) when I try to lay off the button and get it to ‘on’, it goes right out.

        I feel like i’ve got a brake caliper in need of a rebuild; the thing hasn’t been used in so long those valves inside the box are maybe just stuck. Maybe it’s cheap enough to just buy one and put that in, or maybe i’ll have to try a teardown, but before I do that I thought I’d see if you had any ideas?

        Thanks in advance.

        • Hey, Bennett. First, I’m totally with you on the “fix it yourself” kick. I work on my own cars, Sea Doos, house, etc. whenever possible. Although, the one difference is that if I do something wrong and my car breaks down, I coast to the side of the road. If I do something really stupid with a gas valve, things can get ugly QUICK. 🙂

          That said, I’m not a fan of busting open those valves. I’ve never done it myself – maybe it’s easy, but the risk vs. cost vs. benefit comparison just never seemed to be worth it to me. Obviously the thermocouple replacement got you farther (congrats!) and your thermopile is putting out decent mwatts, so the valve is probably the only culprit left. However, I’ve noticed that it often takes me holding down the pilot for a good while before I can turn it to on. How long are you holding it down before attempting to turn it? I don’t know WHY waiting is necessary, I just know that it is.

          • Bennett

            Thanks. I’ll probably look into a replacement (though I overcame that risk/reward calculus the first time I changed out the brakes on one of my bikes, and haven’t looked back). If the cost is too high I might rethink, but for now, replacement is probably the route i’ll go.

            As for the waiting issue, I think I’ve figured that out, from having the meter on from first ignition. As heating the probe is what generates the juice that’s needed to keep the valves open, the hotter it gets, the stronger the output, till it gets high enough to trigger the valves. From there, waiting longer doesn’t make any difference (though as you discovered, to some degree more is better). Since the average user isn’t going to monitor the voltage output, and doesn’t really care why, they just say wait for a minute or so, which is plenty to get it where it needs to be.

          • Bennett

            now i’m getting more confused/frustrated. I was starting to look for a replacement for the control, whatever it’s called, but now i’m seeing readings out of my pilot only 250 mw or so. sure, it didn’t work even when i was getting 500 mw, but now i figure even if i drop the $100 or so on a new control unit, i’m still not going to have it working. like i said, frustrating. i’ve been playing with adjusting the height of the thermopile, but not really getting any improvement in the output, and adjusting the pilot adjusting screw on the control unit that i have, but that’s not getting any stronger output either. i did notice insulation scraped off where the wire comes through the sheet metal and retyped, but nothing changes. still, i guess i need to buy both parts and try again. agree? alternative theories?

      • geneva

        Steve I am so grateful that there are still men out there that doesn’t even blink at the notion to just do the guy stuff…..and thank you so much for the free info on repairing/caring for your fireplace. Going to start by ckeaning the thermopile first before repacing it. Was baffled that there was no thermocoupling present on my Superior gas fireplace…..that’s cuz this model didn’t come equipped with one. The thermopile serves both the pilot and burner to release the gas necessary to operate either one.Thanks again!

      • paul

        Just wanted to thank you, worked like a dream.I am in chicago and we are experiencing a vicious cold snap, much appreciated

        • That’s great, Paul. Glad you were able to fix it and stay warm!

      • Peter Martens

        Hi Steve, a big thank you, I just read the DIY for the gas fireplace resolve yesterday, as I had same symptoms in one of my rental units and I followed your steps to a T and voila, after a little elbow grease with a fine wool cloth to clean the thermopile all works as it should.
        The DIY was well put together and I appreciate your blog.


      • Enrique Vargas

        Thanks for the DIY. Ran into your site by random search and I’m glad I did. I’ll bookmark you for future visits. Thanks again!!!!

        • Shalyn

          Hey Steve!
          First and foremost, I really enjoy your site and found that all your DIY tips and information extremely helpful! So, sorry if this is a bit long but I want to make sure you get all the information in hopes you can help me out with my current ‘situation’ on our Odesa ventless gas fireplace. The fireplace has been working great these past couple years but here lately say in the past couple months, it would be on working fine for anywhere from 10min/1hr or 3+ hours, than all of a sudden the pilot light and flame would cut out. So today I wanted to try and surprise my boyfriend before he got home and possibly fix it

          • Shalyn

            it looked apparent that it was just a matter of cleaning the thermocouple and thermopile, which I did. Well then I thought since I have the “logs” off I might as well clean those suckers too and make it look like brand new ( eager beaver over here)… Well low and behold, my dumbass didn’t realize the logs are not just for show as they are apparently “vent free gas logs” and before it even ‘dawned’ on me I had already ran them under water for a minute (I didn’t use any cleaners or soap, thinking I was being careful) and I think I did a huge no-no (so to speak). Now, my question is if their is any possible way I can dry them out somehow or am I SOL

          • Hi, Shalyn. I hope your BF appreciates the effort, even if the logs got soaked. 🙂

            I’d try just letting the logs sit out in a warm dry location, and maybe put a fan on them to speed up the process. If they didn’t disintegrate after getting wet, then they should dry out fine and be usable. Let us know how it turns out!

          • Shalyn

            Oh my goodness

          • Is that a good “oh my goodness?” 🙂

          • Shalyn

            Dang… I had a bunch more but not sure where it went… Anywho… It was…oh my goodness this has been the best news yet today Steve !! Haha… And no the logs are both in tact!… I did notice some yellowing on the towel they have been sitting on since it happened but I would assume that’s just residual from the grime, dirt, phosphate and soot build up as my bf has never done any maintenance since he bought this place 3 years ago. Ok we definitely have a fan I can put on them to help. But would it be ok to put a small mini floor heater towards that general direction to per say “speed up” the drying or would that not be a good to put heat on them until they air dry? … As us women, are always looking for ways or “proper” shortcuts to speed up the process with the same efficiency! Plus, I would love to have it all put back together before my bf gets home and live and learn from this ‘lovely’ (hint of sarcasm) mistake.

          • Shalyn

            Sorry for the piece mail. It looks like my ‘fun faces’ we’re breaking up the messages. Oh, and so I take it, it is ok to go ahead and ignite the pilot and the light the flame now before I get the logs back in their proper install places. Correct? Also, how long can you typically having thr flame going without the logs?

          • Hi, Shalyn. I wouldn’t attempt to light the fireplace without the logs in place. They are necessary to spread the flames properly. Just wait until they’re dry. The mini-heater won’t do any damage to them (they’re designed to get hot), but make sure you don’t do it in a way that could damage anything else or start a fire with nearby paper for fabric. Maybe use a blow-dryer?

    • Tom

      Thanks for the info. I could not find a thermopile at Lowes, so I just tried cleaning mine after I read your article and it worked like a charm. You save me $50! THANKS!!

      • Those are the success stories I love to hear. I don’t mind giving $50 to a hardware store, but ONLY when I HAVE to! 🙂

  • Great find for me. All the tips worked just as described. Fireplace is ready to go just in time for Christmas. No $150 repairman required. Impressed my wife too.

    Thank you.


    • Glad to hear it, Rolf! And isn’t impressing the wife with handyman skills really what it’s all about? Merry Christmas! 🙂

  • debbie

    Hello! … of course just after Christmas and on one of the coldest days – our Regency fireplace insert just stopped throwing off heat. I have been desperately trying to fix this myself and it appears that we have the same issue as above with the pilot light on – but no heat is being thrown. I am about to attempt your cleaning of the thermopile but would like clarification of “closed the shutoff valve on the hose that fed gas to the unit (VERY important)” …. can you please go into detail about how to do this and where I may find this valve. Thank you. Debbie

    • Hi, Debbie. It’s the main valve (probably with a yellow or red handle) that’s connected to the silver-colored gas hose that comes out of the wall underneath the fireplace. Hope you get it working!

  • Thank you Steve, but I looked all under the unit and found the silver coloured gas line, but there is not anything attached to it or the bronze coloured one. I searched all throughout the underneath and did not find anything connected to any of the lines. I did find a device that resembles a light switch/dimmer. It is a round knob that is, I swear, identical to a wall light switch/dimmer. I tured that all the way counterclockwise until I heard a click. It is attached to wires however and is on the left side of the unit underneath with wires entering a black box on the sme side under the unit.

    • That sounds like the fan switch – it turns on a fan to blow warm air once the fireplace reaches a certain temperature, and you can turn it to adjust the fan speed.

      Gas has to be coming into the unit somewhere. If you can’t find the main cutoff valve for the gas line coming in, it’s possible to do it safely if you KNOW that the switch that says PILOT, ON, OFF is switched OFF, and I mean you need to know it without a doubt, and verify that the pilot light goes out when you turn it to OFF. Then clean the thermocouple, re-ignite the pilot, and see if that fixes things.

  • Debbie

    Our Fireplace is a Regency P36 direct vent if this helps. I am attempting to send you three photos from under the unit to see if you can decipher where his hidden valve shut off would be. The dimmer switch still has me very confused as well since we have never had a light in the fireplace.

    • It’s not a light – it’s almost certainly the rotary speed control for your fan. Have you gone to the Recency website and downloaded the manual? It’s the first hit on Google when you search for “Regency P36.” Page 34 shows the main S.I.T. valve (it’s possible you don’t have a shutoff valve “upstream” of this one), so just make sure that the Gas on/off knob (item 1 in the diagram on that page) is OFF and the pilot light is out. You should be good to go from there!

  • Debbie

    Sorry Steve, I did not receive your last post before I posted my previous post to this one. The fan switch sounds about right for the dimmer … just looks very Mickey Mouse-ish…. I was talking to my brother who works at Napolean and we discovered that thte shut off valve is most likely in an area I cannot see or get to as ours fireplace is a corner unit and the gas line comes in to the house, then is covered by the fireplace unit. I am going to take the glass off now – so hopefully I will be okay and be able to to write back … if not – I am in heaven hoping no one else will buy a Regency Fireplace!

  • Debbie

    YAY!!! …. I am still here! AND it worked!!! Thank you so much Steve!! I cleaned all the little posts with sandpaper and a damp paper towel.

  • Debbie

    Steve, I am so sorry to write you again, but I am hoping you can help me further as I have run into another snag now. The wire (assuming it’s the power wire to the fan) somehow was catching in the fan when it attempted to come on. THe pilot light, fan and everything went off. Almost like a safety switch went off. Now I have cleared the wire from the fan and it is working now – but I cannot get the fireplace to light again. The pilot light comes on but is very very dim. Then after waiting over 5minutes, I slowly move the valve to the on position and the pilot light completely goes out. I turned off the pilot, the fan and the thermostat on the wall. I was going to try it again after leaving it for half an hour in the all off position – but am wondering if you have any other suggestions?

    • Well, first – glad the cleaning worked, and bummer about the wire! Without being there to tinker with it and see what goes where, I’m not able to give advice you should really depend on about where that wire goes – which is important with anything that burns gas. It’s possible that there is some sort of safety switch that got yanked, and you need to find out where it connects. Check through your manual to see if there’s any mention of that. It could also just be a dirty thermocouple… but the fact that you got it to work today leads me to believe it’s something else. I’d go through the manual or even call Regency. I bet they’ll walk you through it on the phone.

  • Debbie

    Thanks again Steve. I tried Regency first thing this morning – as it stated in our manual that we had a limited lifetime warranty … but they were closed today and would not be back to work until wednesday. As well I called a Regency dealer who stated that we actually do not have a warranty … so I wrote Regnecy an email and have left it at that for now. It turns out that the wire that was intruding on the fan was the wire attached to the Tpth and TP. I am assuming what happened was it did have an emergency shut off and shut the whole fireplace down. I made sure the wire was fine without any damage to it and then unscrewed both wire attachments and took the wires off their places and then screwed them back on again. I also shut the whole fireplace off again including the fan switch and wall thermostat as well as the pilot. Then after ten minutes tried it all over again .. and Voila!!! Everything is working again!! With this as our main heat source and this being New Years Eve, I want to thank you so very much for sticking with me on this and replying to my questions. I can now unbundle from my massive layers of clothing and socks and take back the heaters my neighbours lent me. Take care and Happy New Year indeed!! – you not only gave me back heat – but also saved me a service call and tons of cash as well.

    • Sounds like the fan pulled the wire loose for the thermocouple connection. That’s what heats up to tell the gas to keep flowing and keep the pilot burning. Rechecking and reconnecting everything was the right thing to do. Glad you got it working – and Happy New Year! 🙂

  • grant

    Awesome blog, soo many great tips, points, opinions, etc., however, now I have spent well over an hour and it is side tracking me!!
    Maybe you can assist, my pilot won’t light, just went out last year. When I push the button/igniter underneath the unit to light it, I can see a small spark, but that is it, very small. Do you recommend I clean the TH/TP. It is hard to tell if the pilot switch is off or on.
    Other details, there is no wall switch just a remote (Ireplaced the battery), and a gold key like knob outside the unit(assume gas valve). Is it safe to just take the glass off and start cleaning the TH/TP since there is no flame?
    I’m on a roll, this weekend I was able to fix our furnace the flame went out on it, so cut the power cleaned the flame sensor from all the carbon build-up and now it works better then it has in over 3 years, just in time for the deep freeze we are having!!

    • Yep – my guess is that it’s the thermocouple. It prevents the pilot light from staying lit. Give it a good clean (you won’t hurt anything if that’s not the problem) and see if that does the trick!

  • Doug Shild

    Hi Steve, great article! I’m hoping you can help me… I have a wall furnace and the pilot light will stay lit, but the main gas will not flow. There is a high-low knob on the unit that has a wire going to a thermopile on the bottom of the furnace, in the room air. There’s another wire coming out of the thermopile going to the Honeywell valve. There’s usually a click noise and the main gas flows when I turn the knob, but not now… Any idea what I can do? I’m assuming the thermopile is bad, but I’m not sure how to replace it since most of the websites talk about TP and TH connections on the valve, but I only have the 1 wire going to it. Thanks again for the help! Great blog!

    • Hmm… I’m not familiar with the Honeywell valve, and so I hesitate to advise you to fiddle around with it too much. If it’s one of the Honeywell 24V valves, there there’s no thermopile at all — the electricity to open the valve comes from an external source. The “click” noise you mention also supports that theory, since that’s usually the sound a solenoid makes when it opens. So unfortunately, the advise in this post won’t apply to your valve. My guess is that the electrical contacts to the valve that supply power to the solenoid (which can often oxidize and/or fall off) may be dirty or damaged. Remove all the wires (take note of where which ones go) and use some electrical contact cleaner. If that doesn’t do the trick, you’ll probably need a professional to swap out the valve.

  • Mike


    I have a Hampton H27 with the programmable thermostat. Pilot is ON. I can turn on the stove manually with the burner control but its not coming on via the thermostat. Likely the thermopile? thanks Mike

    • It depends on what “manually” means. Generally, the thermopile powers the valve, so if it can turn on (regardless of how), it’s probably OK. I’d check the connection from the thermostat to the valve to make sure it’s closing.

  • Awesome info! Helped me with some DIY troubleshooting. I have a question, when I check the voltage on my Thermopile, it’s fine at 570mv when fully heated by the pilot flame. But the voltage drops to only 180mv as soon as I switch on the “Main burner” switch. The main burner lights and so far is staying lit, but I wonder if there’s not a short somewhere causing the voltage to drop. My pilot has had a hard time staying lit (as well as the other burners) so I wonder if this is a hint as to why it has been shutting down. Thanks!

    • If the pilot light won’t stay lit, that’s more likely the thermocouple instead of the thermopile. As for why the voltage drops when the main burner fires, that’s strange… unless for some reason the increased heat is somehow overloading the thermopile.

  • Colette Vidal

    hi Steve,
    l have an Empire wall furnace and it has been working fine for the five years or so since it was installed. This morning however, l woke up to a cool apartment and l quickly realized that it was off (as the pilot light was off ) and l got really worried because l thought about the gas leaking out since the supply was on. Couldn’t smell gas at all. So l shut off gas supply and then re-lit the furnace following the usual procedure. It went right back on no problem. But now l am worried about leaving the house in case it goes off again. l suppose there is a safety device that shuts off the supply since l couldn’t smell gas. Could you suggest what the problem may be. There weren’t drafts during the night as my windows are closed obviously (it’s -18 celsius outside. l live in eastern Canada. l would appreciate your opinion on this. lt has never happened before, Thank you,

  • Rainey

    Thank-you so much for your help!!! I cleaned the thermopile all by myself (following your careful instructions about turning the gas off) and got my fireplace going again – worked like a charm and saved me some cash! Lorraine.

    • Glad to hear it! And congrats on the DIY success! 🙂

  • Zafar M.

    Hi Steve. I have an electronic ignition valve fireplace. The module can produce a spark at the Ignitor terminal, but there is NO spark at the pilot location. The wire to the pilot looks solid and the wiring harness looks fine. Could there be a buildup on the ignitor electrode that is causing the no spark issue? The gap between the eletrode and pilot shroud is 1/8″. Thanks.

    • Absolutely. Clean everything well (both sides of where the spark should arc), check connections, and give it a go!

  • Michael A. Hess

    We had a Regency U39 Free Standing unit installed just a little over two months ago. Yesterday we realized it was cold and the pilot light was off. It would relight and the main flames would ignite but then it would go out shortly there after.

    This morning I remove the three flame cap over the pilot light orifice. I cleaned it out, clean all around the orifice and cleaned off the thermocouple and thermopile. Reassembled everything. The pilot light would light. It would take between 1 and 2 minutes before the pilot would keep a sustained flame. Then I could turn on the main burner. It would fire up. It would work from 1 – 5 minutes and then there is a pop, the flames go womp and it shutsdown. I go through the same process again.

    I did this several times over 2 hours. Then suddenly the burner stayed on. It went through cycles turning on and off with the blower and everything seemed fine. This continued for 6 – 7 hours. Then a night fall it start all over again. When it pops off the pilot appears to still be on it is just that everything shuts down.

    My non-expert guess leads to several possible problems.

    1. Bad Thermopile.

    2. Weak gas pressure that doesn’t allow for a strong enough pilot flame. (I say this because some times when trying to ignite the pilot there doesn’t appear to be enough gas to light all three flame jets from the orifice.)

    3. The S.I.T. valve is bad.

    I had called the business that installed it but they stated they are busy and it might be a day until then can get to me. Do you have any suggestions of what I can easily test to help narrow down the problem for me or the service tech?


    • Hmm…. I’d say the weak gas pressure is the least likely, and the valve or thermopile being bad is the most likely. If there’s a pop or click before the main burner turns off, then that’s probably the sound of the main gas valve closing – so either the thermopile is telling it to shut off when it shouldn’t, or something else in the valve is closing it when you don’t want it to.

      However, the fact that it shuts off after running for a while also tells me it’s possible that it’s temperature related. Perhaps your unit has some sort of thermal sensor that shuts off the gas if it gets too hot (which might be possible if it’s not vented properly). But the pop before the failure is what I’d try to figure out – that’s going to be the key to tracking down the culprit.

      • Michael A. Hess

        I agree with the gas. I did the following test. I get the pilot light going, which as I mentioned takes like 2+ minutes before I can release the button so it is self sustaining. That seems too long to begin with. The next step would be to turn the valve to the ‘on’ position so that the main burner could fire up. Instead I just left it in that position used to start the pilot. In that position the pilot stays lit for 30+ minutes. That indicates to me that it isn’t the thermocouple.
        However even after that length of time with 15 seconds of turning it so the main burners would come on. They came on and then whoose it all shuts down again.

        Then this odditiy. I have a main switch on the unit for the main burners. It can be set to On/Off/Thermostat. It doesn’t matter what position I have it at. Even if it is set for the main burners to be off the moment I turn the pilot knob from pilot to on with the pilot lit the main burners come on.

        I’m really leaning toward the S.I.T. Valve being bad.

        I think it is beyond me at this point. I need to call the repair rep to look at this.

        • Great job using logic in your troubleshooting — and also for knowing when to stop and say “time for a pro to check it out.” There’s always a point at which guessing isn’t worth the risk to blowing up your house. 🙂

        • Patrick

          As l am having the same issues as yours, ( pilot on, then fireplace on with a beautiful blue/orange flame) and then after2-5 minutes the flame became weaker ( light blue) and the pilot is becoming very weak as well and then it shuts down with a very audible “CLICK”… So what was your outcome/diagnosis if you don’t mind to share?


  • Sandra R

    My gas valve, newly replaced, is leaking propane and I turned off the gas to the fireplace. Now the fireplace store and the propane company are playing the blame game on the reason. The store says the propane company blew out the valve by setting the pressure too high on the pressure regulator they replaced. The propane company says its a bad valve…any ideas??

    • Smart call turning off the propane feed. Don’t mess around with it. I’d pressure both companies to step up, and hopefully one will. 🙂

  • Tom Keegan

    Hi Steve
    I have a gas fireplace that is about 40 yrs. old. When we moved in 2 yrs ago ,we had a pro come here to check it out. He diagnosed a bad thermo couple. I recently was looking for a brand name on the fireplace (could not find one) when I smelled gas. The gas detector also found gas. Pilot light is not working so gas valve should not be allowing gas to enter. Isolated gas line with a shut-off since there was not one even at the appliance and turned off supply. I will try what I have read on your site about how to clean and test current but not sure if valve is the problem with smell. Unit is 36″ with a fan on each side to draw air in from room and then vent back into room from top at center.Fans are turned on by wall switch which is suppose to start the process of heating up. Single wall flu pipe runs to roof. Is it possible there was debri in the line causing vale to be partially open when it should be closed. Can it be cleaned or new valve. I am very handy. In the process of remodeling 2nd house but do not have much knowledge of fireplaces. THANK YOU very much for any info.

  • Amanda Morris

    Hello, I am pretty sure that I need to clean my Heatilator’s TP, but I can’t get my glass off ha ha.but that is not my main question (Ill have to work on that). There is a wall plug (socket) in the unit with 2 plug-in spots and a 3 pronged plug. I have had this unit off with the pilot light off and gas off for a couple of years. Main heat is broken so tried to re-light. Pilot light on like a charm, wall switch on, won’t light. Wall switch for blower fan on blower does come on. I remember a few years ago that it would not light and my Dad (Engineer ha ha) switched the spots the plug was in and it started working. So I switched the spots and the fan starts blowing automatically. I plugged a light into that spot and the light came on automatically, but when I plug the light into the other spot the light does not come on and does not come on with the wall switch. Could the socket be the problem? I could swear that initially the fan came on when I flipped the wall switch when the pilot light was on, but now it won’t come on when plugged into the original spot(before I moved it today) when the wall switch is flipped. It seems like this is wrong somehow. I have it all unplugged now with the gas off. Thanks for being so nice and answering people’s questions!

  • Graham Evans

    Hello Steve
    I have Valor Inset Gas fire with the rear Fan Flue.
    I replaced the Thermocouple last year (the fire is 10 years old now) after it kept cutting out.
    This cured the problem.
    Now 12 months on the fire has suddenly cut out and won’t start again.
    Thing I have noticed is the audiable ‘click’ you normally get when pressing the ‘on’ button for the fan is almost non existent now…..and sometimes the fan will not operate.
    Presuming the thermocouple has not failed again, would it be likely that the solenoid valve is the culprit ?
    I can only think of that or the air pressure switch which sits in the rear of the flue housing.
    I am an engineer by trade and have had the fire apart a few times….just wondering If its worth trying to remove the solenoid and open it up to see if its repairable as they are not cheap to replace ?

    Any thoughts appreciated.

    Regards G E

  • Pingback: Anonymous()

  • John Sylvester

    Hi Steve,
    I have a Majestic gas fireplace, with direct rear venting, that came with a new house 8 years ago. There is no fan or thermostat, but there is a wall switch. The pilot stays lit but the burner goes out after 5-8 minutes. After reading your newsy blog, I suspect the thermopile. I plan on cleaning both thermopile and thermocouple and trying again. If problem still exists I’ll check them both and perhaps replace one or both. Am I on the right track? Please give me your thoughts.

    • Hey, John. Yep – I think you are on the right track. Come back and tell us if this fixes it (and I really think it will). I think your thermopile simply isn’t generating enough electricity to keep your valve open.

  • John Sylvester

    Hi again Steve,
    I’m getting back at ya after cleaning the TP and TH as you suggested in your very informative blog, and your concurrence on focusing on the TP. Before using my multimeter, the problem was solved and the burner stayed on during my one hr test. Thanks much for your help. BTW, what’s a S.I.T. valve?
    Thanks again, John

    • I believe “SIT Controls” is a popular manufacturer of gas valves, and that’s where the name comes from. But if anyone else reading this has a better answer, please post it! 🙂

  • herb

    Hey, thanks for the post. I’ve replaced my thermocouple in the gas fireplace (not too hard) but the pilot light still will not light at all.

    Assuming all gas connections are open and working, igniter works (looks to be sparking ok) and thermocouple is installed correctly, would a bad thermopile keep the pilot light from lighting? It just will not light, never mind stay lit. The thermopile is a bit dirty so I will attempt a cleaning first. Thanks!

    • Hi, Herb. No, a bad thermopile shouldn’t prevent the pilot from lighting. All it does is power the valve. If the valve is set to the pilot position, then it should allow a small amount of gas through fuel the pilot light… but only if the thermocouple senses the pilot is lit. Have you verified that you’re following the proper lighting procedure for your unit? Sometimes you have to hold stuff in, or at the proper position, etc. It can get like the Hokey Pokey. 🙂

      • herb

        Thanks. While I was cleaning the thermopile I also tried to clean up the pilot light area a bit too, but I still don’t think that’s the problem. I smell gas when I press the pilot light for 30 seconds as the manufacturer instructs, but when I hit the igniter repeatedly the spark will not light the gas.

        I got frustrated and did something really crazy and, with the pilot valve depressed, held a butane lighter to the pilot light area (instead of using the igniter). Propane gas coming out of the pilot light opening would light with the lighter in place,
        but when I pulled the lighter away it would not stay lit. it was as if there was not enough gas coming out of the pilot light opening to stay lit. Could this be a bad SIT valve? Just curious – I’ll probably call a pro for whatever comes next as it looks like the simple problems have been ruled out.

        • Hey, Herb. Yeah… sounds like it’s time to call in a pro. Bummer. But better safe than sorry once you’ve eliminated the easy stuff. 🙂 Let us know what it turned out to be!

  • James Wade

    Thank you so much , if I had found your article before now it would have saved me a lot of time reading other articles , the internet is a fantastic place to find information but you have to enter the correct wording . Your article could not have explained thing any better , it was clear , easily understood , and without all the BS that other people put in . I am on my way to my daughters home to check her propane fireplace , I believe there is a thermopile problem , and some blockage in the pilot line, I can’t thank you enough for your great post ,Jim Wade.

    • James Wade

      Thanks again , I could have not done it without your post , checked and cleaned thermopile and thermocouple , cleaned out the pilot burner , the gas was not reaching the igniter , all is well .

  • I left my pilot on this whole year rather than turn it off during the summer to test if I’d have better luck getting the fireplace to light and it seems to have definitely helped.

    However, I’m experiencing this season that the pilot will stay lit, but the main burner will often go out while the fireplace is on. If I tap on the fireplace, the burner will re-light. Ever heard of this? Is this indicative of a faulty valve?

    • Hey, Axlejc. My money would will be on a dirty (or faulty) thermopile. Sounds like your thermocouple is fine, in that it allows your pilot to stay lit. I’d clean the thermopile first and see if that helps the main burner issue.

      • Jason

        Wanted to leave a follow-up. I had wondered why tapping the stove would cause it to re-light. After being annoyed that it would turn off seemingly at random, I wondered if the problem was mechanical — perhaps the rocker switch to turn the burner off could be defective and therefore not contacting (but the vibrations could jar it into contact temporarily). I started by checking the wire connections on the back of the switch and found them to both be loose. After pushing them on tighter, the stove stays on all the time now as it should.

        • That’s awesome, Jason! Glad it was something you were able to fix!

  • Ed

    Having a bit of a problem .. Was getting a real low reading on my Thermopile….89 -100, and slightly lower ..slightly when the thermostat was off. Just replaced the Thermopile and getting the same low readings. Could I have gotten a bum new Thermopile? Or what else is causing this? Could the Pilot Light be too strong on the Thermopile? Would adjusting that solve the problem or do I just have a bad valve.

  • Juan

    Hi Steve, had a chance to read your useful information and kind replies to us fireplace sufferers :).
    I hope you can help my case: I’m trying to start my fireplace and get ready for our brutal Minnesota winters and I just can’t get the pilot to light. I have done this many times in the past so I know the process but this time something is just not right. I rotate the gas valve , I turn on the electric switch from the wall, I push down the pilot knob for a long time and strike the ignitor repeatedly. I can see nice and long sparks but the pilot light just doesn’t ignite. I don’t want to mess with the thermocouple or thermopile as they should not affect the process I’m trying to start (just get the pilot to light). I can’t hear any gas and I have waited long enough for the line to bleed and the gas to start flowing…is there any way to check that the gas valve is working? Any way to ensure that when depressing the pilot knob gas actually flows? Do gas valves ever get “stuck” preventing flow? Also, I see there is some interesting wires going from the main gas valve assembly to some sort of a safety or on/off limit switch located by removable vent panel…do fireplaces have some kind of system to allow them to run only with the lower panel in the upright position?
    Your input and feedback is greatly appreciated.

  • Pat wells

    Your directions were right on. Thanks for saving me some cash.

  • david


    excellent work on this thread.
    finally got rid of the ” whoosh ” because i now understand the way the entire gas fireplace assy. functions.

    saved a ton of $ by not having to call in a tech and replace the entire part for $100.00



  • Stephen Grant

    Good explanation and clear instructions. Same general symptoms (been getting progressively worse over the last year or two and now not coming on at all) so I followed the steps closely, measuring just slightly under 400mA. But after I cleaned the thermopile with fine sandpaper and re-lit, now I’m reading only about 200mA. Ever seen that before? I’m apparently not a very good thermopile cleaner.
    If I have to replace the thermopile, is it a lot more work i.e. do I have to remove all the logs and other bits to disconnect it? can I replace the thermopile or the TP/pilot nozzle assembly?

    • Stephen Grant

      Actually, no need for a reply. It just needed a bit of time. I left it stand for 20 minutes with the pilot light burning. Came back and flipped the switch and presto the fireplace came on. Continues to work great this morning. I measured the TP and it’s generating 800mA, so I expect to have dependable service this winter. Thanks again for your post.

      • That’s awesome news, Stephen. Congrats on the successful DIY fix!

  • Thanks Steve – I just Googled “thermopile clean or replace” and got this perfect info!

    I have been having the exact same problems with my Vermont Castings Jefferson NG stove since last year, including sporadicunreliable lighting of the main flame, the whooompf when it did start, and the 350mv reading, which really worried me that the valve being stuck was the issue and not the thermopile. After cleaning the thermopile thoroughly, which took a couple rounds, it seems to be working fine now. So you seem to have confirmed what I did was correct.

    Also, I read that thermopiles only last a couple years on average – I wonder if this is just because they are dirty and they get replaced instead of cleaned? Why do they wear out? Any thoughts?

    Are you going to post more details on the thermopile/thermocouple changeout? – looks pretty straight-forward, but I wonder about the gaskets (are they included – if not what should I get and are they difficult to fit?). It would be great to know how to do this since it can take a while for a repairman to come out and it is expensive even though not too difficult if you understand the stove/fireplace.

    Thanks again.


  • David Day

    Thanks for the info, my fireplace is working like a charm now. I cleaned the Thermopile and thermocoupler with a fingernail file and all is good. The thermopile voltage stayed the same before and after the cleaning, .520 but now it works. Thanks.

  • Dave

    Had symptoms like others with fireplace probs. Pilot would light but not main flame then pilot would not stay lit. Cleaned both thermopile & thermocoupler. Viola. Worked like a champ for hrs. Went to shutoff with the wall switch and nothing. Main flame and pilot still lit, Had to manually shut off pilot light to stop the fire. Now when pilot light switch rorated to PilOT position(normally push-in and hold to light then rotate to on) pilot stays lit even when released and at ON position main burner lights regardless of wall switch. I think I may have gotten the TP and/or TC out of alignment with pilot light?? THX in advance

    • dave

      Disregard. Had remote switch to ON. (DUH)! Wall switch now controls fire as designed. Happy Wife equals happy everybody. Thanks again for saving so many of us $$$$.


      • Hey, Dave. Great news! I’ve done that same thing with my remote switch. 🙂 If you haven’t already, check out my review of the SkyTech 5310.

  • Ihab

    Excellent article. I just wanted to use a millivolt honeywell thermostat to control my fireplace. i see the switch to turn it off and on is connected to the tp/th and th screws on the fireplace. can i just get low voltage wiring and connect them to the screws, then connect to the thermostat? or does it need to be connected to a on/off switch. Next challenge is to see what slots they connect to on the thermostat…R, G, b…is it a crapshoot or is there some way to figure it out.
    Thanks in advance


    • Hi, Ihab. You’re right – that switch does nothing but touch the tp/th and the th screw together, meaning you can use any sort of low voltage relay or dry contact closure control to close that circuit. A millivolt Honeywell should work fine, as long as (like you said) you can figure out which wires fire when it calls for heat. If it’s a heat only thermostat, you’ll likely use the R and the COM wires. You can also check out my Skytech review if you wanna try something fancy. 🙂

  • Keith

    Hi Steve – I have a weird problem. The main burner on my fireplace will not light when it is near or below freezing. It will though when it gets warmer. In either case, the pilot light will light when I turn on the wall switch. It’s in the 50’s today so I when I go home, it will probably light. What do you think it can be? Thks, Keith

    • I’m still gonna guess the thermopile, and that maybe the cold is somehow making it less conductive. Have you tried cleaning or replacing it?

      • Keith

        Hi Steve – I haven’t replaced or cleaned the thermopile yet. Now I’m wondering if water is getting in there somehow and freezing. Can that happen? When I had the problem last week, it rained the day before then went below freezing that night. It wouldn’t light the next day. Yesterday, I ran it when I got home from work becasue it rained for 3 days straight and it got into the 20’s overnight. It lit this AM when I tried it. My thinking is that by running it, maybe I got rid of the water that got in there. What do you think?

        • It shouldn’t, but that doesn’t mean it isn’t. Your chimney cap should be stopping water from entering, and water getting in is a rare occurrence. Rule it out if you can, but my guess is it’s probably something else.

  • John Tarves

    Didn’t notice this mentioned in your discussion; At the Furnace Supply I was told its important to clean all the wire contacs because of the tiny voltage involved, its easy to foil its passage.

    • Absolutely right, John. Keeping all your contacts clean is never a bad idea!

  • Eric N

    Steve, after looking at numerous sites for nearly an hour, including wading through all of the “call a professional” posts, I finally found your post. I have been trying to troubleshoot if it was the thermopile or thermocouple on my gas fireplace and your information saved the day.

    • Awesome. Gotta love that feeling when you hit the switch and it works! 🙂

  • Mick

    If the pilot flame is not adjusted high enough or thermopile is not located properly, the thermpile may not generate the proper voltage, so one should check that the thermopile is well engulfed in the pilot flame.

  • Munir

    Hi Steve,
    Great website. Went from being clueless to well informed in a very short time.hope you can help with this one. last night I turned on the basement fireplace for the first time this winter and it smelled pretty weird for a while and then it shut off on its own. Never smelled like that before. now I can’t get it to start again. the pilot light is on and the thermal pile millivolt voltage is about 600 mV. voltage does not change when I flip on the switch. Is it safe to take a Bent paper clip and short the TH THTP points to see if the switch is bad? also the knob used to adjust the flame never quite made any difference. Bad valve? We have an old HeatNGlo supreme XT. Thanks!

    • Hey, Minur. Yep – jumping those connections is fine for testing. It’s a low voltage connection, so it won’t “bite” you. And if the knob doesn’t make any difference, then yes – it’s possible you’ve got a bad valve.

      • Matthew

        Steve, my furnace only works when I jump the TH THTP connections with a paperclip, as Munir, above in this thread, commented.

        My question is, what does that tell me is wrong?

  • Carmella

    Hello– quick question– after testing we ended up having to replace the thermopile. That was a pain cause it was calked in. Anyway, now it works but the gas is causing the flames to come out more near the front. It’s like the gas line is out of alignment and were not sure how to get it back in allignment. Any suggestions?

    • Hi, Carmella. Usually, flame location is dependent upon how you arrange the logs. I’m assuming you had to take them out when you replaced the thermopile, so I’d move them around a bit to see if you can get the flames where you want them.

  • david


    pilot lites and stays on no problem.

    thermopile putting out 480 mv with pilot lit

    the on switch has continuity thru it

    burner lites but slow and gas level is low so flames are very small and weak.

    any advice……….?



  • Duane

    Hi Steve,
    My son recently bought a townhome that is about 10 years old and has a Superior gas fireplace. First thing I have noticed since cold what has come is there is a good breeze underneath the fireplace by the gas controls. How would this air be coming in? Also pilot light stays lite but when hitting the wall switch it seems like very little gas in coming and just get a very weak flame from burner. Appreciate any help you can give me on this. Thanks

  • Matthewk

    To the person who had the stuck gas valve where the pilot would only stay lit for as long as you held the button in, and you were getting > 300MV out of the thermopile..

    Please note, I have not tried this. This is totally at your own peril, though I would try this if I were in your shoes…

    If you are going on the assumption that the gas valve has sat for a long time and the electromagnet that the thermopile energizes is stuck and will not engage. I would be tempted to try disconnecting the thermopile, than taping some long lead wires onto the terminals of a regular 1.5V (1500mv) battery, like an AA or a D cell, and connect that to the thermopile terminal on the gas valve a few times rapidly. Tickle it on a bunch of times and than with it in place, see if the pilot will hold if you pres the button and light it. I doubt the 1.5V will hurt the coil in the electromagnet but it may be enough to break it free if it is stuck. If the pilot holds without the button pushed with the battery connected, turn it all off, re-connect the thermopile and see if the thermopile will work it now that it is freed up.

    Good luck!

    • Bennett

      Thanks for the idea. First without the pilot lit I just wired in a 1.5v battery and heard an audible click whenever current was flowing. Sounds like something happening, which would be a good sign the valve is functioning, perhaps? Next, light the pilot and see if it would stay lit with the button released (did something unstick, now it’ll be ok?). No joy. It still went out. Next, light the pilot, apply the battery (testing was the thermopile putting out too little voltage, that extra boost may be needed to open the gate?) but the pilot went out when i released the button anyway.

      so, hypothesis, the click i was hearing wasn’t the gate opening to let gas flow. why else would the pilot go out? Solution? i might be inclined to still think i need to replace the valve assembly, unless someone has a better idea?

      thanks in advance. it’s brushing the 80’s here in LA this week so not really urgent, but while i have time off i’d love to get this fixed finally…….

    • Bennett

      Well, sometimes a good cleaning is, unfortunately, not the answer. Bit the bullet today and bought a replacement for my control and a new pilot assembly while i was at it. after the testing earlier it was pretty clear that the issue was with the valve, but I thought in for a penny might as well go for it all and did both at the same time. And so here we are enjoying a lovely fire.

      by the way, once i had the new control i cracked open the old one, and found a wire (from what i assume was the electromagnet) disconnected inside. i’m just tossing the whole thing, so i’ll never know if that was really the issue, interesting that this might have happened. as it is, total cost was just $150 which still isn’t bad, and should last a few more decades, i’m guessing.

      now, anyone have tips on adding a blower unit to a gas fireplace that didn’t have one originally?

      • Bummer that the cleaning alone didn’t solve it, but congrats on a successful DIY win. That’s still a lot cheaper than hiring someone to swap those bits out. Enjoy that fire — you earned it! 🙂

  • Pingback: Home Maintenance Parts You Should Have In Your House Right Now | Steve Jenkins' Blog()

  • Dave

    Steve, thank-you! I don’t have my voltage tester here so I thought I’d just try and take everything apart and clean the TP and TC just to see… bingo! Works like a charm for the first time in a couple years. I probably created this problem myself over the years leaving the pilot lit during the summer, basically never turn it off. I hope this will now work for a few years to come but if it doesn’t at least I now know what to do. Thanks again Steve, you rock!

  • Kenny Mayberry

    I have a Heatn glow it’s about 11 years old the pilot light will stay lit however when I turn the unit on it will only run for a bout 10 minutes and then shuts off the burner and the pilot light I’ve tried it on the high flame and the low flame it still would only run about 10 minutes and then shuts off everything what do you recommend

    • Sounds like a dirty or defective thermocouple. If cleaning it doesn’t work, it probably needs to be replaced!

  • Roy

    Steve thanks for the details and giving me the motivation to continue with working on my gas fireplace. I had given up a couple of times and was frustrated with the repair guys that show up. Here is my saga.

    The fireplace is 14 years old now and the last 2 years it has been more difficult to get working. I am unfortunately 😉 not afraid to try almost any repair but had stayed away from the fireplace since it was such a cramped work space.

    I called a local repair guy when I could not get it going this year and after 2 hours and $85 he told me to order a new remote control. Seemed reasonable at the time since the pilot was on but really hard to get lit. Another $70 and the new remote seemed to fix the issue but after each time we used the fireplace, the pilot would go out. After reading here I figured it was the thermocouple and found one at the local store. Took a while to install but after installing and cleaning everything the pilot lit right away and kept burning strong for 30 days.

    It just got cold again and I went to turn on the fireplace and it would not turn on. Same exact symptom I began with a month ago. Wiggled some wires and it kicked on so I re-wired everything since it looked pretty sad. No joy but looked better and I removed some unnecessary wiring that had been put in.

    Return to reading here and checked the thermopile and it was reading 220 mV. Cleaned it up and got it up to 275mv but it still would not turn on all the time. I got out the grill lighter and heated the thermopile some more all around and I got it up to 400 mV and the fireplace started immediately. I adjusted the pilot as much as I can but cannot get the voltage high enough so I ordered a new thermopile online since I could not find one locally.

    BTW I reinstalled my old remote and it works fine. I had been misled by the repair guy because he said it was bad and not putting out the right voltage but turns out it is just a dry contact device.

    I feel pretty confident about the thermopile and it should be here next week. Thanks again for the little extra push I needed to tear into it again.

    • Hey, Roy. You’re right — fireplace remotes are simply “on/off.” All the voltage is from the thermopile. Please report back when you get your new one installed. I’m betting it will work great! 🙂

      • Roy

        Hi Steve,
        I thought I would give you the final update. The thermopile arrived last week and I got installed right away was able to get the voltage up to about 350mV which was enough to get the valve to open so that definitely helped but I was expecting a little higher but thought I was good to go. Next day the pilot light was out again and although it lit no problem I could never get it very high or increased voltage.

        About to give up again and I decide to try a clean the pilot orifice. The repair guys said he did it but no matter how much I turn the screw it would not change. So as I was cleaning it and unscrewing, it fell apart in my hands. It was pretty badly mangled so I am sure the repair guy fouled it up then I finished it off. It was hard to figure out which one I needed since the model number did not turn up much but figured it was a SIT model from a Lennox rebrand. The picture I ordered looked a little different but it was only $13 so I figured I cam this far.

        The pilot tube arrive last night and the little orifice cap fit perfectly so on the right track. Went to install and there is not a hole in the sheet metal big enough to get the nut through. When I get to this point in projects I keep going until I fix what I am working on or destroy it beyond all recognition so I grabbed the drill and got after it. Finally made a hole big enough to feed the tube through and everything seem to fit correct. The wife had 911 punched into the phone ready to hit send while I lit the pilot and flame on!!

        The pilot light came on like I have never seen it. The thermocouple was glowing red and I was up to 650mV! I backed off the screw which had been open really far for the old tube and let the pilot settle to about 450mV for now.

        Am I done? Only time will tell. Looking back now the thermocouple and thermopile were probably OK although 14 years old and cheap enough. Unfortunately it has warmed up to 70F outside now so may not be able to use it this year unless we have another cold snap 🙁

        Thanks again.

  • Artis

    Hi Steve, I just found your post and it is Great! My dad was always a great do-iy-yourselfer and taught me the same. I ran into a snag with my LP fireplace and found your site. I cleaned the thermopile/thermocouple (which seems to be one and the same). It seems to be working good! I had lit my fireplace and after about a half an hour it went off (I heard a click in the valve) and I could not get the pilot to stay on when released.
    I cleaned it and it is working well!
    Thanks, Artis

    • Awesome. I love hearing these types of DIY success stories, Artis. Every dollar you don’t pay to a repair dude is a dollar you can save, or spend on something more important. Great job.

  • Brad

    My pilot light is staying lit, but the burner will not light on my Superior direct vent fireplace. I cleaned the thermo pile and it is reading 470-480 mv. I have a wall switch and connected the wires directly and it still won’t work. Any other ideas on what it could be?


    • Hi, Brad. That could possibly mean that 480mv still might not be enough for your valve, or maybe it is but the valve is stuck closed. How long did you let the pilot run before hitting the switch? Sometimes, the thermopile takes a while to build up voltage. If waiting a bit longer still doesn’t work, try to see if you can get the valve assembly out (shut off the gas first) and take it to a local fireplace shop and having them inspect it. That’s still cheaper than getting a repair guy to your house. If they verify that it’s bad and can’t be fixed, you should be able to replace it yourself (you can buy the valve from the shop, but price compare online first so you’ll know if they’re giving you a fair price). Take pics before disassembly, hook everything up slowly, and use a soapy liquid to check for any leaks.

      • As an FYI for anyone else reading Brad’s comments, I just received an email from him saying “Ended up replacing the thermopile and got close to 700 mv out of the new part and the fireplace is working. Thanks for the help.” That’s great news, Brad! Congrats on the DIY fix! 🙂

  • David

    Hey Steve, just wanted to say thanks for posting all this great information. I was having the exact same problem…the fireplace would turn on intermittently and sometimes make that “whoomph” sound when it did light. I replaced the thermopile and the fireplace is back in action! You probably saved me a couple hundred bucks in service fees to have to have a guy to come in and figure out the problem and fix it. Glad you posted the info so I could do it myself. Cheers!

  • Gary Goldberg

    Thanks! Just reading this saved me some money and, more importantly, saved me time, Both my gas log fireplaces failed to light up this winter. After finally getting the one thermal pile off, I thought I’d read up on other solutions. Since neither pilot light would light, I had some Emory cloth and just cleaned up the bedroom fireplace log thermal couple and pile! It works like new! Simple. Now to get the other fireplace log put back together and CLEANED, I’m confident it’ll work also. Thank you!

  • Rherst

    Steve – thanks so much for the detailed instructions. I followed each step, including buying a voltmeter, so I could be sure of what I was doing. After cleaning the thermopile, just as you described, the fireplace works perfectly again.

    Thanks much

  • Eric

    Thanks for your super useful fireplace DIY blog. Learned enough from you to solve my problem and now have a smooth running fireplace. You provide a great resource!

  • cheryl

    we have a older appalachian un-vented propane fireplace heaters model UV-36 we replaced our wall mount thermostat and it turns on but does not cycle you have to manually turn it down to kick off (was set at 72 and was up to 78 )and maually turn it back on(set to come on at 72 was down to 69) any ideas?

    • Hmm… that sounds like an issue with the thermostat. Is the thermostat making a “click” when it reaches the appropriate set point? I’d use a multi-meter to test for continuity to make sure the thermostat is “opening” and “closing” the appropriate connections on your valve when it should.

  • K Warner

    Awesome article! Spent all night messing with my logs and this was the most comprehensive article I found. Even down to what TH on the terminals meant. In my case it turned out the valve was simply stuck as I haven’t used the fireplace in two years. I read on another page the thermopile can be diagnosed by connecting a AAA battery to the TH and TP terminals. Me trying to hold the wires actually tripped the valve several times and it came on. Turned out when I hooked the thermocouple wires back it worked fine. So this may be a good trick to free up a stuck valve. It worked for me as I had cleaned everything and that didn’t work but that 1.5 V freed it all up. Thoughts?

    • That’s great! I’ll add the AAA trick to the article, since that’s a great way to quicky “bypass” the thermopile and make sure that’s the real problem. Congrats on your DIY fireplace fix!

  • Chris

    Hi Steve,
    You just saved me a bunch of money! Thanks. My sweet little propane heater was gradually getting harder to ignite the burner…3,4,5, seconds and whoosh! Then it wouldn’t light. Called the shops and they were a little ‘vague’ but would have the service guy call for a chat and, most likely, a $137 service call (parts extra). I thought it was a simple circuit and couldn’t be rocket science so I found your page. You instructions and cautions were spot on. Ten minutes and a vacuuming later, the voltage on the TP circuit went from 117mV to 175. Lights immediately every time. Thanks again.

  • Jack McK

    My pilot worked, but the full flame would not turn on. I cleaned the thermocouple and replaced the on/off switch. It works fantastic now! I have about $3 and one hour invested. It saved me at least $135, which is what the fireplace repair shop wanted as a minimum charge. I can’t thank you enough.

  • Greg

    Came home one night and my gas fireplace would not come on. After tinkering for a bit, I could get my fireplace pilot to stay lit, but when I turn the nob to “on,” the pilot would go out. I cleaned the thermalpile with a wire brush and plumbers sandpaper cloth and was getting good readings on my volt meter, like above, but still, when I turn the gas valve nob from “pilot” to “on,” the pilot would go out. Thinking about the first rule of troubleshooting (“is it plugged in”), I decided to change the batteries in the fireplace remote receiver which is connected to the gas valve. Viola, when I turn the knob to “on”, everything works again. I decided to change the batteries in the actual remote too as that has given me problems in the past as well.

  • brian

    thanks for the advice! I have add-on gas logs with no electronic controls at all, and was getting a pilot but no ignition. I tried your trick of cleaning the thermocouple and it worked like a boss.

  • Mat

    Steve, great blog. The article on the fireplace TP and TC was excellent.

  • Lisa

    This worked for us too!! Thank you!! Dealer was going to charge me $230 just to make a service call.

  • John

    Heatilator GDST36 Gas fireplace won’t light up pilot light is on. When I turn the wall switch on the burner does not light. Thermocouple has been replaced. If I hit the gas valve with a wrench the burner lights. I am thinking it is the valve that needs to be replaced. I also read that any dust buildup in and around the controls could affect the current necessary to start the burner. Any thoughts? Than you

  • Harold

    I followed your instructions and cleaned the carbon off my thermopile, cleaned up the glass doors, sealed everything back up, turned up the thermostat and I heard the familiar sound of the gas logs lighting up. the whole process took me 15 minutes. I used a wire brush and some fine cloth sand paper. I probably saved $150 bucks for 15 minutes of work. Thanks Steve!

    • These are my fav types of comments, Harold. Congrats! 🙂

  • Dan N.

    Very useful write-up. My thermopile was easier to access than the example. When I saw white crusties similar to the picture I cleaned it up without bothering to break out the multimeter. Viola! Gas valve worked again.

    I would like to add that my fake logs may have shifted a little and the pilot light is configured so that they may have to be correct for a nice even heating of the thermopile. I put the logs back carefully paying attention to the index pins and soot and wear patterns.

    It’s so nice to remember that there are other uses for the interwebs beyond baby animal pictures!

  • cy

    Thankyou so much. It’s my first time to work on fireplace. It’s wonderful. I first cleaned the thermopile with an old toothbrush. The fireplace came back to work. I shut it down again and cleaned it with sandpaper finally in order to for it to work longer. Now, trying several times, it definitely works. Thankyou.

  • yvonne

    Nobody unless they are Gas Safe should have a go at any form of repair on their gas appliances, do all these DIY people know about the importance of gas pressures and soundness testing etc, my advice to any DIY person reading this article, leave ot to the experts!!!!!!!!

    • Yvonne: Some things I do indeed leave to the experts… but some things (like simply scrubbing a thermopile and thermocouple) are well within the capabilities of a careful DIY enthusiast. 🙂

  • al

    can you replace a thermopile with a thermocouple?

    • Good question – the answer is “no.” A thermopile is much thicker, as it needs a much larger surface area in order to absorb enough heat to convert to electricity. A thermocouple is skinny, as it only needs to be warm enough to report “yes – I’m warm!” 🙂

  • Terry

    Good Morning.
    I have replaced the thermocouple and cleaned the thermopile following your directions. But the stove still will not light. I have a nice blue pilot and I have vacumed out the stove. I’m at a loss as to why it won’t light. Please advise.

  • Terry

    I forgot to add my stove is a envirogas28 it is about 14years old.

    • Alex

      The same thing is happening to me, any luck on your end?

  • Allan Reini

    Wasn’t lighting. Read your article. Is lighting. ‘Nuff said. THANKS!!!!!!!!!

  • Rick

    Steve, thanks for the clear explanation. The thermopile is generating 224mv enough to allow the switch underneath the fireplace to work, but NOT the wall switch. Rating states 350mv to 500mv is required. However, I can only find thermopiles online at 250mv to 750mv. Will this higher rating work as a replacement? Thanks.

    • You bet. The higher rating shouldn’t be a problem.

      • Rick

        Steve, just to close off the thread. Just installed a 750mv thermopile and it works just fine, as you stated. it generates 586mv which meets the minimum rating as stated in my previous post. Thanks again for your help and this blog.

  • Mark

    When I turn on the fire place with the wall switch at the start of the season, there is about a 10 minute delay, before I hear the gas, and then the fire ignites. Every now and then, but not often the same thing happens, however most times after the first time it has been burned in several months there is no delay. Any idea what may be going on?

    • Hi, Mark. I’ve experienced the same thing. My guess is that it’s related to the thermopile, because whenever I clean mine it seems to help with this delay before the “whoomph!” Eventually, every thermopile needs to be replaced. If the delay gets too big, I bet swapping out your thermopile for a new one will fix it.

      • Mark

        Steve. After cleaning the thermopile, the delay has gone away and the fire ignites immediately – thank you. What is your opinion about turning off the pilot light during the warmer months when the fire place is not in use? Do you think turning off the pilot light when not using the fire place on a frequent basis will prolong the life of the unit or is it better to keep the pilot light running all the time?

        • Hi, Mark. I shut mine off (I shut off the gas upstream of the valve, actually) and then re-light in the fall. It probably only saves a minor amount of gas, but I like to think it also extends the life of the thermopile.

  • Jeff

    Your blog was fantastic! Thank you! You made it very easy to understand and diagnose. We took off the front of the fireplace, removed the logs to expose the thermopile/pilot/thermocoupler assembly and, sure enough, after a quick five minute cleaning with a brillo pad it fired right up! Again, from two very amateur DIYers we really appreciate your help.

    Jeff & Robyn

    • Man, I LOVE hearing that, Jeff! Here’s hoping that this is just the first of many DIY projects for you. With blogs, YouTube, and forums — it’s easier than ever to get the info (and confidence) you need to tackle lots of projects yourself. Great job in a successful fix! 🙂

  • Derek

    Thank you…cleaning the thermopile and the thermocouple worked like a charm.

  • Ed

    Really wanted to thank you for this post -helped me get my wall furnace started and taught me so much about how it works – sandpapered some rust off of thermopile and got it started after multimetering- saved me some $$ thanks!

  • Krista

    Thank you!! This website I’m sure saved me over 100$ – so clear and easy to understand – awesome!

  • steve

    I am now enjoying my gas fireplace, thanks for your cure. It worked like a charm. Your instructions were easy to follow. I owe you a “cold one”. Steve

  • John

    Thank you!!!!!!!!

  • Alex

    I have just replaced my thermo couple, my pilot will not stay on, I hit the button for more than five minutes and nothing happened. Pilot flame looks strong and blue, my insert is a Travis Industries FPX 34 DVL.
    I understand that the thermopile is responsible for turning the flames on correct? Not the Pilot? or the thermopile is also responsible to keep pilot on as well.
    Any help is appreciated.
    Thank you

    • Hi, Alex. Check the section of the article that starts “If your pilot light ignites but won’t stay lit…” As explained there, the problem is most likely your thermocouple. If cleaning it doesn’t solve the problem, you should replace it. It’s a very easy job, and your local hardware store will have a generic replacement thermocouple for about $10.

  • ALEX

    Hello, thank you for you response. As I mentioned, I did replace the thermocouple, however it’s not staying lit. What else can it be?

    • Ah – I must have missed that.

      You usually have to hold the PILOT button down on the valve for AT LEAST 30 seconds while lighting the pilot, before letting it go. This allows the thermopile to warm up enough to “know” that the pilot is lit again.

      How long are you holding it down?

      • Alex

        Steve, Again, I did mention that I replaced the thermo couple and held downforce more than five minutes, however the pilot is not staying on. Can it be something else preventing the pilot to stay on so spidering I’m holding it down for more than thirty seconds?

        • Sorry, Alex. These comments don’t get “threaded” in the admin interface, so it’s hard to remember what’s happened previously in the conversation. I should just come to the “outside” page to see the convo better. 🙂

          Sounds like you’re doing everything right, and there really aren’t THAT many moving parts! All I can think of is that perhaps while replacing the thermocouple, you didn’t get a good connection on the valve side. if you have a multimeter, try doing a continuity test from one end of the thermocouple to the other, to make sure there are no breaks. Also, double-check how the thermocouple is screwed into the valve. That’s really all I can think of! Obviously you’re getting gas through the valve, or the pilot wouldn’t light at all. If the pilot light is going out even after holding down the pilot button for 30 seconds (heck, I’d even go a minute or two just to be extra sure), then it keeps coming back to a thermocouple problem for me.

  • Bob

    changed thermastat month ago on fireplace evertthing workin ,then nothing ,changed thermal coupling, pilot on but still wont fire up, can here thermastat click but nada, now what ? even cleaned thermopile? Bob

  • bruce

    steve I have cleaned the thermopile fired up the switch and watch the burner ignite only 1/3 across, I have cleaded the burner holes but can smell gas, any suggestions?

  • Steve,

    Thanks so much for writing this. It was so helpful.


  • Andy

    Great article, fixed my fire are saved alot of hasstle. Thankyou!!

  • Joe

    I have a 11 year old Majestic fireplace that is not wired to a wall switch; it only runs via Honeywell remote. A week ago stopped working, except the pilot, so I cleaned everything. I cannot start the fan or flame so I assume the remote it failing. Is this easy to switch out?

    • If both the fan and flame are failing, then yes – I’d check the remote. If you have a standard gas valve, you can test this theory by using a piece of wire or a paperclip to “bridge” the two TH terminals on your valve (thereby “closing” the connection between them). If the fireplace lights, then either the remote sending unit, or receiving unit, is dead. You can easily replace with the same Honeywell remote that you currently use. Or, you can upgrade to something a bit fancier like this Skytech I reviewed. 🙂

      • Joe


        Thanks for the assistance! The paperclip bridge failed too. I can hear a click sound, almost like a breaker popping sound. I also learned my system operates on duel thermopiles, so am i better off replacing prior to addressing the remote?

        • Before replacing stuff, use a multimeter to read the voltage at the valve’s TP contacts (as described in the article) to make sure you’re comfortably generating enough electricity to open the valve when the TH contacts are bridged. If you’re low, then yes – the problem is with the thermopile (or one or both thermopiles in your case). If you’re well over the amount needed by your valve (check the valve docs to know the amount), then the problem is with the valve itself.

          • Joe

            multimeter readings were 550-600. Valve requires more than 100 when in pilot mode, tested well over that. Are there any more tests I can run? Sounds like a valve but the remote failure is perplexing.

  • Jeff Scharphorn

    Steve – Thank you for the helpful information. I have a good Thermocouple and standing pilot with a Thermopile reading of 550 to 600 millivolts after cleaning. The wall switch has good continuity but the gas value still doesn’t open with the switch on nor with a jumper wire. The valve does open when a AAA battery is connected to the TP terminals. Does this indicate the valve is bad or should I still try replacing the Thermopile?

    • If the AAA battery opens the valve, but the thermo-battery (pile means battery in French) doesn’t, then yes – sounds like the thermopile isn’t generating enough juice to open the valve. If cleaning it isn’t enough, time to replace it. May as well do the thermocouple at the same time (since it will go bad eventually). It’s a cheap part, and since you’re taking eveything apart anyway for the TP, now is the perfect time.

      • Bassam Afeiche

        Hi Steve
        I join the multitude of those who praise your blog. My problem is that two of the three pilot flames are strong but the third, supposed to engulf the thermopile doesn’t reach it. I would appreciate it if you could suggest how to solve this problem. Thanks.

        • Hmm… that’s usually an issue with the pilot hole being plugged, or the thermopile bracket being bent into the wrong position. I’d kill the gas to the entire unit, try cleaning out the third pilot hole with a pipe cleaner, and then re-lighting and giving it another shot.

          • Bassam Afeiche

            Hello Steve. Thanks for your reply that I have just seen it. I was expecting it on my email as I understood it when I posted my question 🙂
            The pilot hole is very tiny and I tried to unplug it with a fine wire. It didn’t work. Is there a pipe cleaner small enough to do the job, and where one can get it?
            Thanks a lot.

  • geo6869

    Tried cleaning the TP and TC, and blew out the whole area. Unit has not been operated (not pilot light or gas – LP – in the system) for at least a year. Cannot keep the pilot light going, and it does not seem to be as abundant as the ones shown in various videos from Heatilator. Could this be a gas flow issue? I purchased a 100 lb tank (new) and a regulator at Lowes. This is a ’04 a GCDC80. Do I need a special regulator for this unit?

    • It could be a flow issue, but my money is still on the thermocouple. If it’s not telling the system that the pilot stays lit, it will kill the gas from the valve. If the thermocouple has gone completely bad, cleaning it won’t help. It’s only a $10 part, so I’d say it’s worth the risk of swapping it out before troubleshooting further.

  • Douglas

    Thanks for is DIY post. I followed your directions and it all worked exactly as you said it would. I’m just very happy this was an easy fix to the gas fireplace.

  • Lisa

    You are my new hero. I tried to schedule an appointment to have our fireplace looked at – they’re booked till SPRING. Thanks to your clear and safe instructions, we have a working fireplace after simply cleaning the thermocouple and thermopile! Yahoo! You save me time money and frustration.

    • Booked till spring? Wow. Makes me think a teenage kid could make a couple of bucks in your area with a TC/TP cleaning service. 🙂

  • Angelica Light

    Steve, thanks to you we now have a cozy fire at our beach house in time for Thanksgiving guests. The property manager’s staff couldn’t fix so we did using your very clear instructions. Many thanks for sharing your expertise.

    • You’re welcome, Angelica! Did you gloat to the property manager staff? You earned it. 😉

  • Jason Stevens

    Great post, Steve. Quick question: My thermopile reads 715 mv when hot, but drops to 13 mv when I turn my fireplace to “on” and the fireplace does not kick on. Could the thermopile be bad? Any suggestions are greatly appreciated.

    • Yes, it could be getting to the point (like any other battery) where it can’t handle the “draw” to supply the necessary power to the valve long enough to open the valve. I’d try replacing it before anything else.

      • Dan

        Since using Steve’s excellent primer and advice 8 months ago I have learned that you should only see the voltage drop roughly in half or as Steve say it can no longer support the load (amps). There is of course the chance the load has become too large but start with the cheapest fix which will be a new thermopile every time.

  • Rick

    Thank you. I have a 2 year old Regency gas fireplace that the pilot light would not stay lit. The fire if it did start would burn for several seconds then go out. Simply cleaning the thermopile with fine sandpaper solved the problem. I never would have suspected this because the thermopile did not look sooty or have much if any obvious deposit on it, but it worked.
    Thanks again

  • Mike

    Thanks for the info. It worked like a charm!

  • I’ve had a lot of trouble the last couple of years getting my pilot light to start. It sometimes takes considerable fiddling with the knob while pressing the ignition button and there are times when it won’t light at all. Once the pilot light does come on, the fireplace works just fine. It will also turn on quickly if it has been on recently. Any suggestions what the problem might be? It’s an imported Regency fireplace that we had installed when we built our house 11 years ago, but we’re in Japan so having an “expert” look at it is not really an option.

    • How often are you shutting off the pilot? This should really be something you only do once a year, as the weather starts to get cold.

      It’s normal to sometimes have to CLICK CLICK CLICK the starter a bunch of times to get the pilot lit for the first time. If the fireplace is 11 years old, it COULD be wanting a new thermocouple, which might reduce how long you have to hold down the knob in the pilot position before being able to let it go. It’s a $10 part (does Amazon ship to Japan?), and an easy swap.

      • We have been turning the pilot off each day as that’s how it was originally explained to me 11 years ago and we wanted to save on LP gas costs, which are quite high in Japan. Recently, though, it’s been more difficult to get the pilot light to take. Once it takes hold, though, I don’t have to hold down the knob very long for it to take, so it doesn’t seem like the thermocouple is the problem. I will leave the pilot light on for the month and see how that affects our gas bill.

  • Mark Roberts

    Steve, Thank-you for your very informative blog, we have a Vermont Castings propane stove and every year I have this problem, either the pilot light refuses to stay lit or the burner will not start, our electric furnace went out today so tried to fire the stove. This time the Pilot light would start but would go out the moment I turned it to the on position. I checked the voltage of the Thermopile, it was around 280, I then followed your recommendation and cleaned it with emery cloth and steel wool, The thermopile then registered 315 and she fired right up. I suspect that this borderline voltage required to open the valve so I will look into replacing the thermopile soon. Thanks again, it would have been a very cool night waiting for the furnace repair man to show tomorrow. Cheers.

  • Tracie

    Hello, looking for some advice/help….i have a gas fireplace, 20yrs old, only used maybe about 10 times, hadnt used at all since around 2005 and its now 2014. I decided to use it again, and got it started just fine, fire ran for about 15 hrs “straight”, then I noticed the Flames went out & then shortly after I heard a little click sound and noticed the Pilot Light went out. I have not been able to get FP to work again. I got the pilot light to light, however as soon as i release the control knob, the pilot light goes out. I do hold the control knob in for at least a full minute (which is what my instructions instruct me to do) but when i let go of the control knob, pilot light goes out in about 3 seconds. Any suggestions? I have read alot of posts here mentioning about possible cleaning of the thermocouple, but i was wondering would that really be a possible reason for pilot light not staying lit even after it burned consecutively for 13hrs?

    • Hi, Tracie. Could be that you had a weak thermocouple, and the prolonged heat finally did the trick and killed it. 🙂 Nothing wrong with running your fireplace that long. But if that thermocouple lasted 20 years, then you got your money’s worth from it!

      If cleaning it doesn’t help, just go ahead and replace it. It’s an easy and inexpensive fix. Your local hardware store should have a compatible thermocouple.

  • I have such a fireplace at home and I wasn’t sure how to clean it. Thanks a lot for giving your ideas and suggestions. You’ve helped me a lot!

  • Tracie

    Hey Steve,
    Just wanna say THANK YOU THANK YOU THANK YOU for ALL ur help with my gas fireplace issue 🙂 I got it working AGAIN and I am SUPERRRRR THRILLED!!!!! I was dancing around my living room :). All I did was remove the glass, and remove the logs so I could get to the pilot,thermocouple. Thermopile and I used a scotch brite pad and cleaned it then I got my vacuum cleaner and tried my best to suction whatever grit that was there, put that glass back on, turned that control knob to “pilot” hit that piezo button and held it for 1min and like MAGICCCCCC it STAYED ON!!!!!! And I have MY FIRE BLAZING!!!! I can’t tell you how HAPPY this makes me :). I definitely didn’t have the money right now to pay someone to come in and troubleshoot, so I resorted to the internet and found YOU!!! THANK YOU SOOOO MUCH!!!!! Oh yeah I found another video that I thought was really good that showed me exactly “how” to clean that assembly, I will share that with you later when I get home.

    Have a Great Day/Night and Weekend Coming 🙂

    • J Love

      Great article. Thank you. It gave me the tools I need to try to discover the underlying problem with my fireplace.

      Last year we discovered this problem and our workaround was to leave the pilot on ALL the time and just turn the log flame off and on manually rather than turning the unit completely off when not in use.
      This worked until we had an unknowing person in the house who used the remote control to turn the unit off and now it will not re-start.
      Pilot goes on, then goes off.
      Valor fireplace. No wall switch, remote only. Remote works, batteries in receive module replaced.

      I followed all the instructions here to clean the thermocouple. I don’t have a Thermopile, but a Thermocouple is right there as expected in the flame of the pilot.
      It wasn’t dirty looking, but I cleaned it and the area around it anyway including a fine wire brush and very fine emery board polishing.
      Pilot lights but gas does not come on and as such, a few seconds later, the pilot turns itself off.
      I’ve even tried holding a flame to the thermocouple for longer prior to trying to start it up thinking that possibly it’s not getting hot enough.
      I’d like to TEST the thermocouple with my multimeter, but I cannot access it without dismantling the fireplace from the inside (remove logs/ burner, metal plates below logs, etc). [The thermocouple enters the mechanism in the back behind everything where I cannot even see it.
      Should I just go for it and dismantle this thing? (gas off of course and all the usual precautions).
      I’m no pro, but I’ve installed a ton of stuff and have worked on many a machanical and electrical project (a couple furnaces, water heaters, entire house electrical systems, a gas on-demand water heater, gas stoves, stove parts like igniters, etc, so I’m comfortable with a screwdriver and a multimeter.


      • Heck, yeah. I say go for it! And let us know how you make out!

        • J.Love

          OK, unit dismantled. I thought I’d have to do more than I did, but there was an access panel under the logs and under the first metal plate (there’s a lower metal plate, but I didn’t need to take it off because it has a little access door that allowed me to reach the screw-in place for the ‘other’ end of the thermocouple).

          I’ve ordered online a replacement thermocouple because I damaged this one removing it (the screw nut was completely attached to the business end of the thermocouple, so unscrewing it twisted the metal like a pretzel).

          I have not tested it because it’s dead for sure now.

          I can only hope that the new thermocouple does the trick. If not…well…hmmmm….

          At the moment I have a living room strewn with fireplace parts and am awaiting the mailman’s delivery.

  • Hi Steve……great tutorial……my fireplace is working very well….too well …its flame is BLUE…..i would like it a little dirty and burn Yellow….any suggestions would be greatly appreciated

    • That’s generally caused by not enough contact with your logs. Try moving them around a bit to see if that helps.

  • I had no idea how to do that myself! I thought that I should call professionals and you’ve just opened my eyes! Thanks a lot!

  • eddie

    thank you for the great fireplace video. you saved me a bunch of $$$$

  • Phil

    Hey, this is an awesome tutorial, very helpful!

    We’re having trouble with our wall switch. When we remove the wall switch and connect the wires directly, the fireplace lights and stays lit. When we connect the wires through a switch, the fireplace does NOT light. We’ve tried two switches, but both are standard 120V. Do we need a special millivolt rated wall switch?

  • ymb

    Yes! it worked. I used a toothbrush and a small brillo pad and cleaned it. Thank You I saved money as I did not had to call the repair guy. My husband was very surprised.

  • Albert J.

    My propane stove wasn’t working, from what I read, the ThermoPile (TP) was messed up. After cleaning it, the stove still wasn’t lighting, but the pilot worked fine. IF YOU WANT A QUICK TEMPORARY FIX FOR A BROKEN THERMOPILE, do this (figured it out on my own, not to brag):
    Take a battery, I used AA, but AAA should work. Strip 2 wires partially of insulation and connect the wires to the battery, red to + and white to -. On the bottom of the stove, find the TP circut. Connect Your red to the red in the stove and white to white. If your pilot is on, it will light within a few seconds.
    You will have to touch the wires every time you want to start the stove

    The TP transfers heat from the pilot to electricity and that electricity opens the valves to let gas into the stove. If the TP isn’t working, the heat isn’t tranfered to enough electricity, if at all. The battery does the TP’s job and gives the electricity to the valve, opening it, and making the process work.

    Hope this helped!

  • Donna

    Steve, I just had our FP store service come out ($155 charge) because we smelled gas when our unit was running. The repair person said there was a leak, checked all the connections and then suggested we replace our burner because of hairline cracks (it was under warranty – no charge for replacing). The Heat N Glo unit is 12 years old and we are on LP. They came back and replaced the burner last week and there was an “exhaust” smell which we thought was from the new burner. This didn’t go away (it actually got worse) so I called them out again this week. In addition to the gas smell, the FP is booming when it initially lights and is even louder when the remote turns it on. There is also an increased gas smell whenever it turns on. The repairman said he can’t do anything else. He suggested I call the LP company and ask them to check for gas leaks. Do you have any suggestions? Thanks in advance, Steve, really appreciated all of the helpful comments in your blog!

    • Hi, Donna. I’m just a DIY hack, so whenever there’s a gas smell involved, I tend to leave it to the experts. And I would absolutely call the company and have them check for leaks. Eliminate that possible problem first, and then keep troubleshooting.

      • Donna

        Steve, thanks for your response. The LP company came out today and they adjusted the pressure on the tank and on the house. So far, it has helped both the gas smell (guy said it was probably pooling until there was enough gas to light the burner) and has eliminated the “booming” when it was lighting. He also said we should probably have the regulator on the house replaced since it has never been replaced (our house was built in 1992). He’s pretty sure that the other funny smell was from the new burner. He thought it could take up to a month for it to burn off…we had assumed it would burn off after a week or two of use. His service call was free…he said he gets a lot of calls from his customers who have their FP serviced by this company. He suggested they get an LP gas detector devise!

  • Lindsay

    Hi Steve, My valve to the gas must have been turned too tightly and now I can’t get it open to turn on the gas and use my fireplace! I’ve gone through 2 keys already.. the top snaps right off when I turn it because the valve is so tightly shut. Any suggestions? I’ve tried WD40 but it didn’t seem to work.. just broke another key. Once I get that working, I’ll be trying some of your other tips to see if I can get the fireplace to stay on once I take my finger off the button!

  • Eric

    Excellent article. I had the pilot light working but no gas on my month old natural gas/propane unit. I cleaned the thermocouple and thermopile with no success. I swapped the identical thermopile for the natural gas pilot with the propane one I had been using and that didn’t work either, which ruled out the thermopile and thermocouple. Checked all wires and connections and made sure everything was free of dirt, and everything was ok as it should be for a new unit. I couldn’t imagine the valve being bad already, so I kept following wires back to the starter box. Then the light bulb went off in my head. BATTERIES. The remote batteries were brand new, but I had never thought of the ones in the manual ignition box. There was enough juice in them to make the clicking noise when I clicked “on” on the remote, but not enough to actually open the valve. Popped in 4 new AA batteries and it fired right up. I felt like a fool, but this was mentioned nowhere in the troubleshooting manual, nor in this article. Replacing all batteries(if there are any)should be step one as the easiest fix. But I learned some good info here nonetheless. As a man, I did not admit how I really fixed this to my fiancee, I went with the thermocouple issue instead. Haha

    • DOH! Nice fix, and that’s a good tip to check first. And your secret is safe with me. 🙂

  • Stephen Sensabaugh

    I enjoyed reading the posts from your blog and hoped to find an answer to my problem, but alas I must have a unique problem. I recently replaced my flooring in my fireplace room and had to remove my Earth Stove free standing fireplace that I would guess is 30 years old. I moved it back in with a two wheel dolly after taking out the glass and the logs and put it in place. could I have jiggled something loose in the control valve? After reassembling the logs and the glass, the thermostat wires, and the gas line I tried to light it. The pilot would light and stay lit, but the burner would not light. After reading your blog I checked the volts and I saw I had 180 or so. I cleaned the thermopile, (and my unit only has a thermopile no thermocouple), it only sightly increased the milivolts so I purchased a new one and installed it matching it to my old thermopile. I still had barely 200 milivolts so I cleaned the new one too with some fine sandpaper until the made in Mexico ink was gone. What ever that did, now the pilot would not stay lit when I released the button. I was getting very confused. As a last resort I put the old thermopile in a vice and polished it to a chrome like finish with 400 grit sandpaper. I re-installed it read 400 plus milivolts. I thought I hit the jack pot, but when I turned the valve to on and let it sit for a while and then jumped the thermostat wires together the pilot went off. I tried it again with the same results. could something be ajar in the control valve or maybe stuck?

  • Stephen Sensabaugh

    Hi Steve me again. I just thought of something else. This stove has had a history of erratic behavior, but once I get it working it works wonderful all winter long. I also increased the milivolts a little by turning the pilot light up. I have a new pilot tube assembly ordered, but it is not due here until March 5th, 2015. I think it comes with a new thermopile too. Any ideas I might be able to follow up on or should I bite the bullet and try to find a new control valve?

  • Bill G.

    Steve, I followed your advice on themopile maintenance and it worked perfectly. No doubt you saved me a service call ( I had called two fireplace guys and both didn’t return my call so I embarked on finding a solution on the Internet and came across your site.)

  • Chiefig

    Steve, did as instructed, worked like it was new. Thanks for the blog.

  • Tom Tam

    Dear Steve,

    Last night my fireplace was working fine. However this morning when I tried to turn it on, I do not hear a click sound that opens the valve. Instead, I hear a high pitched squeal? The pilot light is lit, but the burner won’t ignite. Also, my gas log do not have terminals. The TC wire goes to the piezo and the TP heads into the valve assembly. Please advise.


    • I’d start with the easy stuff: clean the thermopile (and thermocouple while you’re in there anyway). Maybe you’re just not getting enough voltage to the valve. Let’s hope it’s that easy!

  • Frank

    I took Steve’s advice and after 2 winters of no flame…I now have flame. I didn’t want to hire someone when I thought it should be an easy fix. Sanded thermopile and while I was in there sanded the thermocoupler. Thanks Steve. You likely saved me $200.00.

    • Brian Kuhn

      Dear Steve

      I just bought a house with a majestic vermont gas fireplace (dvrt36 rp). Wall switch control, no remote. Everything works fine, but the main burner doesnt turn fully off when i hit the switch to “off”. The flames pulse in and out like its trying to turn off but never does. I have to turn the entire unit off everytime when not in use. Any advice?

  • Ev

    Thanks for all the information, but it doesn’t solve my problem. Pilot light comes on & stays on. When it wants to, the fireplace will come on & run for a period of time but not finishing to thermostats temperature. We started of cleaning both thermo coupler & thermopile. With reading your blog decided to replace the thermopile but still got the same problem ????

  • Shannon Konyndyk

    Steve, Followed all instructions to clean TP and TC and they went from reading around 320 all the way up to 620-660! Only problem is my burner is still not igniting. It would seems that the TC and TP are good? Or could they still need to be replaced?

    • Wow – that’s a great jump on the thermopile voltage! But without knowing how much your valve needs to ignite, I can’t tell if it’s enough. Put your tester’s leads on the valve terminals where the thermopile connects (TP and TH). When you hit the switch, does the voltage drop in half? If it does, then your thermopile is probably fine. If it only drops a little, then the problem is with the valve itself. If it goes to zero (or close to it) then the thermopile needs to be replaced. It if doesn’t change at all, then there’s a problem with the wall switch (or the wiring to the switch). I should really add this testing info to the main article. Lemme know what you find!

      • Shannon

        Did test, the reading drop from about 620 down to 340 when I hit the switch.

        • Shannon Konyndyk

          So the thermopile is good, is there a next step I could try? Replace thermocouple? Call a pro? Thanks!

  • Pingback: how to light a gas fireplace | android firmware download()

  • Scott

    Thank you! Your advice worked perfectly, and the fireplace is now working like new! Just had some buildup that needed to be removed with scotchbrite and a wire brush.

  • John Bell

    Great article. Really helped me solving some problems with my old fireplace 🙂 Thanks!
    I hope you enjoy this virtual fireplace as much as I do , when my real fireplace broke I used it all the time.

    • Glad it helped! And thanks for the link to the video. The sound on that vid is awesome! 🙂

  • Scott

    Only thing I have to say is don’t use anything too abrasive to clean the thermocouple or thermo pile. This could scratch the surface and allow the thermopile or thermo couple to collect debre in the scratches and shorten its life span.

    Hvac technician in Colorado

  • Andrew

    Great article. Clear and detailed. Thanks.

  • Hooray!

    But who’s Mike? 😉

  • Deana

    Steve. No problem lighting the pilot light but main burner wouldn’t ignite. I cleaned the the thermocouple and thermopile and for one glorious afternoon the fireplace worked. However, this morning the main burner again won’t ignite. Time to replace the thermocouple or could it be something else?

    • Probably time to replace the thermoPILE. If the pilot stays lit, the thermoCOUPLE is fine. A new thermopile (which generates the power to open the gas valve when it’s time to fully ignite) will likely to the trick! However, since the parts are so cheap and the tough part is disassembly, I’d just replace both at the same time do you don’t have to touch it again for years. 🙂

  • Mike

    I just moved into a house with an older Napolean GVF30. The pilot works fine but the main burner was not getting any gas after turning the valve switch to on regardless of hi/low setting. After reading up on forums like this and the little info in the owners manual I went ahead and jumped the main valve terminal connnections between 1 and 3 and the main burner received gas and fired up. Removing the jumper killed it which I expected. I do not see any wiring at all for a thermostat or remote switch. Can I just leave terminals 1 and 3 jumpered and use the gas valve knob to control the fireplace if I don’t want to use a remote switch?

    • Yes you can. It will be identical to just having the switch in the “on” position all the time.

      I would, however, recommend installing some type of switch at some point. 🙂

  • It COULD be, but I still have my money on the thermopile. You might also check to see if your setup has additional switches (if it has a glass door that opens) or a safety override that shuts things off if it gets too hot. But I might go ahead and replace the thermopile, just in case your valve wants higher voltage.

  • rob mccolley

    Great post, Steve. I just used CLR to dissolve the crust on my thermopile. Ten minutes ago, I didn’t even know what a thermopile was.

    I’ll wait a few days before attempting to ignite the fire, just in case CLR was exactly the wrong thing to use…

  • alice

    Hi Steve, so we’ve determined that both parts are bad, so who do we call now to come replace them? I called a local HVAC company and they said they don’t do that kind of work…

    • Seriously, it’s very easy and you CAN do it yourself. Find a YouTube video that shows how to replace a thermopile and thermocouple. Just follow along, take all safety precautions (turn off the gas valve to the fireplace before you start), and you’ll be done in less than a hour.

  • Frank

    Thanks Steve for the website, its new years eve in northern Illinois and thought we would stay home and bring in the new year next to a warm gas fireplace, Went to fire it up for the first time this winter season and no fire, just the glow of the pilot light, Did a google search and found out that the thermopile probably had to be replaced until I found his site; Cleaned thermopile and wa la, gots fire now, Thanks again for the website!!

  • Hi, Craig. Sorry to hear it’s not working… especially in the middle of winter. I don’t have any experience with the auto-igniting versions, so I’m not I’m not more help. If you decide to continue troubleshooting on your own, make sure to take all necessary precautions (shut off the gas, etc.). And if you get in over your head, get a professional in there. When I’m working with gas, I’ll only go so far before I cry “uncle.” 🙂

    • Craig

      Thanks Steve!

  • The heat from the pilot light is converted into a small amount of electricity by the thermopile itself. Thermopile literally means heat (thermo) battery (pile).

  • Dave

    Awesome. That was so well explained and easy to follow. Fireplace working again now & wife happy I did it. LOL Thanks very much!

  • Tara Schubauer Reynolds

    Thank you so much! Thanks to your helpful advice are gas fireplaces up and running again. We live in Colorado and are due to get a storm here in the next day or two and thanks to your advice our fireplace is working. Please keep up the good work!

  • Wow, Maria. I’m SO glad you got your detector working. So so glad!

  • rob mccolley

    Hey Steve, cleaning the thermopile didn’t work. Can you address the dangers & benefits of short-circuiting the two connections on the valve? For me, those are the ledes to the TP and the power switch.

    • Hi, Rob. I can’t recommend short-circuiting the thermopile connections. I’d just go ahead and replace it.

  • Hmm… that’s weird. I’d check to make sure you weren’t simply closing the switch connection, which fires up the unit. Has the fireplace worked before? I’d triple check the wiring.

    • Chris Broadbent

      I have had it for about nine years. Funny after doing that a couple of times everything is now working perfect. Weird… Maybe the gas valve was stuck closed for some reason and just needed a little prodding.

  • Diane Perkins

    Thanks, Steve. My husband cleaned the thermocouple with sand paper, and now the pilot light stays on. I was able to cancel the service call to our propane company and saved some $$$.

  • Bob Jones

    Is it possible my gas valve could be faulty? Thermopile seems fine and the pilot light is lite, but still no fire. When I turn on the fireplace I can hear a click in the valve and a little gas comes out.

    • Yes, that’s totally possible. They will wear out eventually.

      • Bob Jones

        Thanks for the reply! Took it all apart and found a dead spider blocking the gas jet! That’s what I get get for turning off the pilot for the summer.
        Sent from my iPad

        • LOL – wow… I would have put that VERY low on the list of possible issues. But you get full points for not giving up. Enjoy your toasty fire! 🙂

  • Hehe… Not possible? Bah. Thanks for keeping MY man card intact, too. 🙂

    As you so expertly demonstrated, it’s a matter of physics. Increase the surface area that is converting heat into electricity, get more electricity… which is EXACTLY what you did. Great job.

  • James

    I just wanted to take a minute to thank you for your post on this subject. I was extremely helpful to me in diagnosing my Radiance Gas Stove problems. I do have a quick question, does the length of the electrical leads coming off a Thermopile make a difference in the end result Voltage (because of resistance)?
    Thank again for your help.
    Warmest regards.

    • Hi, James. Technically, sure… but nowhere near as much difference as the surface area and conductivity of the thermopile itself. Unless they’re like 20 feet long, I doubt the length of the leads would create enough resistance to prevent enough voltage from being available to open the valve.

  • Songbae

    So helpful! I have a technician here but couldn’t understand what he was trying to explain until I read your post!

  • Michael Carpino

    Thanks for the instructions Steve. I just replaced both the Thermocouple and Thermopile on our Gas Fireplace. The fireplace wouldn’t ignited at all so I first tried to clean the carbon off of both of them. Unfortunately it only allowed the fireplace to ignited for less than a minute. So I bought both the Thermocouple and Thermopile and installed them. Flipped the switch and “whooph”. Works perfectly. Thank you so much!

  • Chuck Wanamaker

    Steve – thanks for the information. My fireplace would fire up when I turned it on then go out in about 20 seconds. I cleaned the thermopile and the thermocouple with a brillo pad. Works like a champ now. Saved at least a $150 after multiple phone calls to repair guys. Thanks again.

  • LOL – I love the “what could possibly go wrong” question. 🙂

    • rob mccolley

      I get it.

      But considering my considering (as evidenced by the length of time between entries in this very thread) it’d be hard to argue that I wasn’t excessively cautious.

      Plenty of things can go wrong with home heating/natural gas, sure. It’s flammable and toxic, yeah.

      But in this one circumstance, the only thing that can “go wrong” is one safety mechanism disliking the input it gets from the other safety mechanism, and disallowing dispersal of the combustible agent.

      INstead, the two parts agreed that their terms had been met, and allowed the nice warm fire to ignite. All is good.

  • Let us know how it turns out!

  • Congrats on the fix. Stay warm! 🙂

  • Have you done a millivolt reading on your thermopile?

  • JM

    As with Don below, I did as Steve recommends: a good vacuuming then brushing the thermopile to get the white residue off. Also gave the pilot a good brushing. My 15 year old gas fireplace is now good as new. Saved me a service call and unnecessary part replacements. Cheers, Steve!

  • Mark Rawkins

    Hi Steve
    I have an Majestic DVR36 RN direct vent gas fireplace. Cleaned thermopile and thermocouple.
    The pilot stays on but main burner does not light. The thermopile has a reading of .575 and should be enough to run main burner. Can it be a faulty thermopile or gas valve. Fireplace is 20 years old???

  • TerryG

    Hey Steve, thanks for the post, VERY helpful. I have a HeatnGlo Tiara I-b gas stove heater that I purchased 8-10 years ago and have had the EXACT problem you describe. Per your (very helpful) instructions I I have cleaned my thermopile and thermocouple multiple times over the past couple years, but eventually the problem returns, with the WHOOMPH start when the main burner kicks in, which causes me great concern. I have also spoken with the installer on several occasions, and have done everything they suggested, which is basically the same as what you have instructed. Owners manual says TP should be >325 mV, and mine reads 425-450 mV, so well withing nominal value. I would need to remove the unit from the top pipe and wall to replace pilot assy., which I wish to avoid. Might you have any other suggestions before doing so?

  • Harry Truman

    Hi Steve. I agree with your DIY philosophy, there are many rewards to DIY including lifelong learning and empowerment (problem solving), wealth building (money savings), and keeping you out of trouble. In the modern world of planned obsolescence, installation of any new appliance immediately has associated with it the problem of maintenance. My first house was a fixer-upper, I did 150 projects (documented every penny spent), everything except replace the furnace, roofing and stucco. BTW this was lost on my divorce judge, he gave the house to my ex and forced me to pay alimony so she could hire professionals to do everything I did from cutting the grass, shoveling snow and making improvements. Apologies to all you female DIY’s out there!