Low millivolts from a thermopile

DIY: Gas Fireplace Won’t Light? How to Clean your Thermopile and Thermocouple 240

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!

I'd love to hear from you! Comment below:

240 thoughts on “DIY: Gas Fireplace Won’t Light? How to Clean your Thermopile and Thermocouple

    • Steve Jenkins Post author

      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.

        • Steve Jenkins Post author

          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!

      • 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

          • Steve Jenkins Post author

            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

            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?

          • Steve Jenkins Post author

            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!!

  • 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

    • Steve Jenkins Post author

      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!

  • Peevair Pomotional Items

    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.

    • Steve Jenkins Post author

      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.

    • Steve Jenkins Post author

      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

    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?

    • Steve Jenkins Post author

      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.

    • Steve Jenkins Post author

      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!!

    • Steve Jenkins Post author

      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!

    • Steve Jenkins Post author

      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

    • Steve Jenkins Post author

      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.

  • axleyjc

    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!

    • Steve Jenkins Post author

      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.

  • 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.

  • 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?


    • Steve Jenkins Post author

      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.

        • Steve Jenkins Post author

          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??

  • 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!

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