Furnace - Thermocouple | Repair and Replace

[@AmreSupply]

*Note* The thermocouple voltage can be tested with a multimeter. We explored this in more detail in this video on Water Heaters. The steps to test and the resulting voltage is the same. This will help you determine if the thermocouple is working correctly. kzbin.info/www/bejne/g6mZo413br6rrJY As well it can be helpful to clean the connection between the thermocouple and the gas valve. If there is corrosion on the threads of the gas valve, then it can reduce the voltage from the thermocouple. Using vinegar and a q-tip you can clean the threads. If you've installed a new thermocouple and it still isn't producing enough voltage, then it could be a weak pilot flame. This could be because it is not hitting the right part of the thermocouple, or the pilot assembly could be dirty.

[@kathycarroll9102]

I have a gas heat stove called a thermolure and it doesn't want to kick off. I just had a new roof piton and they fixed the vent on the chimney. It was kicking on and off fine, what do you think is wrong?

[@kathycarroll9102]

Roof put on, I meant.

[@johnfarmiloe4223]

This guy is right! Worked like a charm. Thanks bro

[@AmreSupply]

@@johnfarmiloe4223 You're welcome!

[@sgardner4313]

Wow, thanks so much! I feel like I understand my furnace so much better, and those video just saved me a $200 service call on one of the coolest days of the year! You're a good humanwho deserves heaven (if it exists)!

[@AmreSupply]

Thank you, we're just happy to hear that this video helped you out! Cheers!

[@RideFar]

I'm suspecting a dirty or bad thermocouple in my older standing pilot Burnham boiler. This is the best how-to information I've found in several hours of research. Excellent job, thank you! :thumbsup:

[@AmreSupply]

Thank you! We're glad you found the video helpful!

[@Red-Eagle]

I got the same boiler gas furnace as you do RideFar. This video def helped me troubleshoot my furnace issue. Couldnt figure out why the furnace wouldnt fire up.

[@busster1075]

I couldn’t just go on with the rest of our evening without posting a HUGE THANK YOU! After spending an hour trying to unsuccessfully reignite the pilot, I found this video and viola! Keep up the great work, we home owners are grateful!

[@AmreSupply]

You're welcome, we're just grateful that these videos are helping people!

[@BigDozer60]

Excellent video, sir!!! You explained the step-by-step procedure very clearly, so that everyone can get what it is you're doing here. And because of this video, you've saved me some cash. I have a cottage up north with a gas furnace from the 1960's, I think it's a McClaren but I'm not sure? I've owned the cottage for 15 years now and this old furnace is a TANK and I've not had any issues with it at all, ever!!! But tonight I did...Lol...The pilot light would not stay on at all. So, I found you here on YT and I followed your instructions and things didn't change at all, but that's ok because it was filthy back there, so I cleaned everything up and there was build up on the Thermocouple as well, so now it's clean as is the limited compartment I have to work with in there, as is all around the furnace. So, things are cleaned up nicely, just no furnace. I was speaking to my neighbor about this issue, after I followed your instructions and he had a tip for me as well, which I'll pass along to you here. First off, he thinks it's now time for a new Thermocouple based on my results. I also showed him your video and he was also impressed how well you explained things. Afterwards, he suggested that I try a trick someone told him about a few years back. Turn everything off so we're safe and not going to blow up the place...Lol...Next is to heat up the Thermocouple with a match or lighter for about 30 seconds, then turn on the gas, turn the dial to PILOT and go through the starting procedure. I did that and sure enough, the furnace started and I turned up the heat and the burner kicked on and then there was HEAT!!!! It worked like a charm....for about 15 seconds...Hahaha...Then the furnace shut off again. I assume that is now 100% proof that the Thermocouple is pooched and I need to replace it? What do you think of that little trick with heating up the Thermocouple with a lighter for 30 seconds and then going through the start up procedure? If it's something that I shouldn't pass on to other people with furnace issues, then I won't do that at all. He had the same furnace issues as I have now and it was another neighbor that told him about heating up the Thermocouple with a lighter, then turning the gas back on and go through the start up and his results were the same. Anyway, I'd like to thank you for an excellent video and I did SUB your channel and I'm sure once I go through your video's I'll find more useful items there for me to check out!!

[@AmreSupply]

Thank you for sharing!! If you have a multimeter, you can actually measure the voltage of the thermocouple to verify if it is working correctly. This video on water heaters shows the steps which are the same for standing pilot furnaces: kzbin.info/www/bejne/g6mZo413br6rrJY Another thing to check is that there is any corrosion at the threads that the thermocouple screws into the gas valve. If there is corrosion then it will reduce the voltage and prevent the gas valve from opening. Cheers.

[@roybarksdale9710]

Thanks to your video I was able to repair my gas boiler for less than $9.00. My wife was demanding that I call someone after my furnace stopped working in the middle of the night and we woke up to 60 degrees inside. I know I would have paid over $200.00 if not for your video. Thanks again.

[@AmreSupply]

You're welcome Roy, we're glad that the video helped you fix your boiler!

[@AW-qv2lh]

Thank you for these. My furnace still isn’t working BUT now I know I’ve done everything I could. It’s 30 years old so I’d say it’s had a good run. Thank you again though. At least now I can competently discuss the issue with a repair worker in my area.

[@AmreSupply]

You're welcome Amanda! 30 years for a standing pilot furnace is completely reasonable. If you do end up getting a new furnace it will likely be a high efficiency with a forced draft. These work in a slightly different way so if you're curious on learning more, you can see how it works here: kzbin.info/www/bejne/qoevpX2tnt1glZo

[@luigim162]

I can only repeat what's been said- well done and clearly explained!! Thank you!!

[@AmreSupply]

Thank you Luigi!

[@kwkuma]

Very helpful 👍

[@AmreSupply]

Glad it was helpful!

[@DavidReason-ko5kx]

This was an exact replacement for the old one that lasted about 10 years. kzbin.infoUgkx7yWIKcrbA9KMHkGSfcgxW2lsjHT6B8Sh The top of my mitigation tube by my roofline was just a 90 elbow which allowed too much debris to fall down into the fan, eventually ruining it. Without this issue, I bet it would have kept running another 10 years. When I replaced this fan, I added an extra elbow joint so the top tube now it does a 180, which should solve that problem. The radon guys around here wanted to charge me a $300 diagnostic fee, then parts/labor (probably close to $600 total). I installed this all by myself in about an hour for the cost of the fan; it would probably be even easier/faster with two people. FYI the manufacturer's warranty greatly differs depending on whether you install it yourself (1 yr warranty) or have a licensed installer do it (10 yrs).

[@AmreSupply]

Great to hear!

[@xDrariculx]

This video just saved me from calling a heating company at 3 in the morning. I can't believe the fix was this simple, but I have two young kids and the nursery temperature warning was going off, so it was either figure out how to fix it or spend the $50-$100+ to call someone in to fix it for me. Thank you!

[@AmreSupply]

You're welcome Anthony, we're glad that the video helped you get your furnace working again!

[@soccerkittens5998]

Thanks for the help I was able to replace a coupler with no problem in about 15 minutes also I love your voice great for passing information and teaching

[@AmreSupply]

You're welcome, we're glad that the video helped you install a new thermocouple.

[@dar322sk]

An excellent video! Thank you so much for doing this. I was pretty much convinced that the thermocouple is the problem we’re having, but am not sure now (I cleaned it twice and yesterday replaced the old one with a new one. Looks like that wasn’t the problem. Our old Lennox furnace (TH8320up1011) acts normally sometimes (and the house seems to be is staying at the set temperature), but we’re experiencing sporadic, inconsistent issues. For example, sometimes the flames light and run for a few minutes (without the blower coming on), then the flames turn off. A few minutes later the blower comes on (without flames), then IT turns off after a few minutes.

[@AmreSupply]

Thanks for watching, we're just happy to share some good info. If you have an older furnace without an advanced control board, then you likely have a fan limiter or a fan limit switch. This is a more simple way of controlling the timing of the blower fan. Some models have one switch, other models will have an upper and lower switch. If you can find an exact match then it could be worth replacing. There are universal replacement options as well: www.amresupply.com/part/14961119 There is a rating on the side of the limit switch. These can be tested for continuity but keep in mind depending switch you might need to add heat with a hair dryer or heat gun to check if the switch will actually open and close as needed at the set temperatures. This video talks about the limit switch but is geared towards forced draft furnaces kzbin.info/www/bejne/ZqfEkKqsrMt2eKM

[@dar322sk]

@@AmreSupply Thanks again for your help! I realized just yesterday that the furnace model I provided in my message was incorrect (that was the thermostat model). My furnace is a 37-year old Lennox G12Q3-137-3. Can you tell which part I should be looking at to address my issue?

[@AmreSupply]

@@dar322sk Parts lists are supplied by the manufacturer and with an old model like that you likely won't find an exact match or a current list for that model. From what you described the problem could be from the fan limit switch. You can however match by specifications.The links in the previous reply should help.

[@dar322sk]

@@AmreSupply Again, thank you. Two last questions. After sitting next to the furnace yesterday to monitor what's happening, I see there's a pattern. Cycle 1: Heat comes on without the fan for 2 minutes, then stops, Two minutes later, the fan starts without the heat and runs 1 minute. Then nothing until 20 minutes later. Cycle 2 (normal?): Heat comes on for 1-1/2 minute, then the fan starts (with heat) and runs 2 minutes, when the heat then turns off. The Fan runs without heat for 1 more minute. Then the first strange cycle starts again 20 minutes later, followed by the second cycle that seems to be a more normal one. This seems to be the pattern. Does this still sound like the limit switch, and do you think it's possible to either adjust or clean the switch? Thank you!

[@AmreSupply]

@@dar322sk It doesn't sound like the thermostat would cause that sort of behavior since the thermostat just calls for heat and doesn't control those sequences. First make sure that the furnace filter is not dirty, and there is nothing blocking the exhaust vent. If all of that is good, then it could be a faulty fan limit switch or control board. Most switches use a bimetallic strip that heats up and bends to disconnect power. This strip wears out overtime, the metal gets fatigued and won't perform the way that it should. Most switches can't really be adjusted.

[@morgancameron8793]

Thank you so much! My house was 45 last night! This worked!

[@AmreSupply]

You're welcome Morgan, we're glad that you got your furnace heating again!

[@vicespin]

Great Video. I replaced the thermocouple like you showed. WORKED!! You saved me 300.00 Keep up the good work.

[@AmreSupply]

Thank you, we're glad that the video helped you replace your thermocouple and save some money!

[@tomscrony]

These video really helped. That was the issue with my Virginia Casting gas fireplace. Thank you.

[@AmreSupply]

You're welcome, we're just happy to help!

[@jimfischer4703]

Great video. Tenant with no heat. Omg. Old Fraser Johnstone gas furnace. Here we go! Thx so much.

[@AmreSupply]

You're welcome, we're just happy to help!

[@BurritoBalladBBd]

This was a life saver! Thanks for the clear and concise explanation.

[@AmreSupply]

You're welcome, we're just happy to help!

[@krimsonkoolaid1]

Thank you this has been seriously helpful

[@AmreSupply]

You're welcome, we're just happy to help!

[@sankark6114]

Thank you so much!!! This helped me to fix my heater today, especially during the winter time. 😌

[@AmreSupply]

You're welcome Sankar, we're glad that the video helped you get your furnace working again!

[@geekynerdenhoffer]

excellent video, i love the graphics and descriptions. i will give this a whirl before buying a new one.

[@AmreSupply]

Thank you, we're glad that you found the graphics helpful!

[@Liefpj]

After 13 yrs i have only fixed the fan belt myself $5. But then yesterday I had to spend $350 for a pro to tend to the Thermo coupler. Not bas for a 1970s furnace in -20c winters.

[@AmreSupply]

Thanks for watching. That is not bad for 5 decades of use.

[@Bonezswiss]

This is best find about this on KZbin thank you so much you guys!

[@AmreSupply]

You're welcome, we're just happy to help!

[@DanielIsaq]

Thank you so much it's really helpful

[@AmreSupply]

You're welcome, we're just happy to help!

[@Rich-ic8wl]

Excellent video - very professional! Thanks!!

[@AmreSupply]

Thank you John! We definitely try to make every video clear and professional. We're glad you found it helpful!

[@vincentpiselli6193]

My Thermocoupler needed to get installed in a vertical direction. I installed it at a slight angle and still had to call a service for help since the pilot still went out. Make sure it is not leaning forward toward the gas outlet tube of the pilot. If it is too close the coupler pin won't heat properly and the pilot will still turn off. Tiny rookie mistake but it made all the difference.

[@AmreSupply]

Hi Vincent, thank you for sharing your experience. There is a lot of variation in how thermocouples are mounted and yes the position can make a significant difference in how it works.

[@PostUp_Time]

*best video available*

[@AmreSupply]

Thank you for watching!

[@quynhboitruong1682]

Thank you so much for your thorough video instructions!!!!

[@AmreSupply]

You're welcome, we're just happy to help!

[@xironminerx]

Are thermo couples universal size for furnaces?

[@AmreSupply]

@@xironminerx Thanks for watching. The thermocouple itself will be the same size but the lengths will differ. So when install a new thermocouple, match based on the length of the tubing.

[@AvnerRosenstein-ULTRA-LXV]

This is the best tutorial on youtube honestly. I do have a question. Is the longer "thermocouple" end that goes into the main burner portion supposed to fit loosly into that nut? If not how do you get it to be tightly in as I see no way of tightening nut to cause the long rod to stay in tightly. In other words even though the nut is firmly on the unit, the long rod can literally just be pulled directly out of it.

[@AmreSupply]

Thank you we're glad that you found it helpful! There are thermocouples that push in and screw in. The ones that screw in might have a coupling or a piece that wedges in. There might be a little bit of variety and not all furnaces will be the same. If the thermocouple has been changed in the past then it's possible that a piece is missing. The thermocouple kits often come with some mounting hardware so that could help make it more secure. You can see some of the mounting hardware in this example: www.amresupply.com/part/1980-824-THERMOCOUPLE-24-inch-UNIV-KIT

[@AvnerRosenstein-ULTRA-LXV]

@@AmreSupply I have a screw-in version and it came with that smaller black piece in the photo. Does that fit over top of the rod and sit flush with the screw portion before inserting it into the housing or does it somehow go inside the screw portion? This is the one thing that pretty much every video or tutorial doesn't really mention or at least show.

[@AmreSupply]

@@AvnerRosenstein-ULTRA-LXV It's been a few years since we've filmed this series and the furnace that we filmed with had a different setup and didn't include those pieces. From what I can see in the picture, it would make sense to slide on the nut first, then the triangular piece then the smaller black sleeve. The smaller black sleeve should press against the triangular piece and the nut to help secure the thermocouple.

[@AvnerRosenstein-ULTRA-LXV]

@@AmreSupply that's what I ended up doing. I placed the tiny black piece on the end of the thermocouple rod to secure it within the screw. The only problem I had was that the black piece was easy to push forward if not careful. Thanks a ton for your help!

[@AmreSupply]

@@AvnerRosenstein-ULTRA-LXV You're welcome, we're just glad that you got it all sorted out!

[@GloriaGooden-Davis]

1:13 Excellent. Easy to understand and follow. Thank you.

[@AmreSupply]

You're welcome! We're glad that you found the graphics helpful.

[@dsmlink1271]

Thanks just pulling it and cleaning fixed the problem appreciate it!

[@AmreSupply]

You're welcome, we're just glad that the video helped you out!

[@gregfisher8205]

My thermocouple just needed cleaned. Thanks for the help !

[@AmreSupply]

You're welcome Greg!

[@MMAEXTREMEBRASIL.]

Thank you very much

[@AmreSupply]

You're welcome, we're just happy to help!

[@TheBigtimz]

TY! This helped me.

[@AmreSupply]

You're welcome!!

[@zappasmustache]

Thank you for this presentation of not making this simple repair intimidating.

[@AmreSupply]

You're welcome, we try to put this same sort of clarity into all of our videos!

[@christanicholson6692]

Thank you!

[@AmreSupply]

You're welcome!

[@malku65]

Very clear, thanks!

[@AmreSupply]

You're welcome!

[@2QRh6g1I]

Got charged $160 diagnostic fee + $120 parts/labor to fix a bad thermocouple. Wish I had watched this video first and then done it myself!

[@AmreSupply]

Thanks for watching. Its always good to know a bit more about the repairs. For some people that cost is justified as it gives them the peace of mind. For others like yourself the repair is simple and can be done in a few minutes. Considering that your water heater also has a thermocouple, you'll be prepared for any future repairs. Cheers

[@themechanic4953]

Ya and the part it only 8 bucks just bought one today

[@asadabrahamian4749]

Well explained!

[@AmreSupply]

Thank you, we're just happy to help!

[@asadabrahamian4749]

Well, I replaced the thermocouple unit on my Burnam burner. But the pilot does not stay on. It may ne something else? What else could be bad or corrupt?

[@AmreSupply]

@@asadabrahamian4749 Thank you for the update. Following the steps in this video you can test the thermocouple to see if it is producing enough voltage. This video is on a Water Heater but the same principles apply: kzbin.info/www/bejne/g6mZo413br6rrJY If the voltage is low in an isolated test with a new thermocouple, then it could be an issue with the position of the thermocouple in the pilot flame, or a weak pilot flame. Cleaning the pilot can sometimes help. Alternatively if the voltage is good, it could be an issue with the connection between the thermocouple and gas valve. If there is corrosion on the threads on the gas valve then it can reduce the current from the thermocouple. Cleaning the threads can also help.

[@thealaskanbyrds]

Really well done video with great explanation. Very nice work, thank you, now to warm up my hands and remove this failing thermocouple! Thank you.

[@AmreSupply]

Thank you Brian, we're glad you found the video and explanations helpful! Hope the repair went smoothly!

[@ransfordmclean1121]

Awesome job bro.

[@AmreSupply]

Thank you! Cheers!

[@doomsdayzalinsky7910]

Very helpful. Thanks once more!

[@AmreSupply]

You're welcome, we're glad that you're finding the videos helpful once again!

[@ELF1977]

Thanks Vance. I'm going to try cleaning first.

[@AmreSupply]

You're welcome Matt. Another thing to try cleaning is the thermocouple screw and the part of the gas valve that it screws into. This can be done with vineger and a small q-tip. Any corrosion or rust can reduce the voltage and can also create problems.

[@RedMango55]

I still have an ICG furnace. 40 years now. Yes, will get it replaced soon though.

[@AmreSupply]

Thanks for watching.

[@andykam6744]

Thank you

[@AmreSupply]

You're welcome!

[@Tobez]

My thermocouple is definitely dirty. Glad to know it just needs a cleaning(hopefully). Thanks for the video

[@AmreSupply]

You're welcome Tobez, we're glad that you found the video helpful! If you still run into problems you can actually check the thermocouple for voltage, the steps are the same as this video on water heaters: kzbin.info/www/bejne/g6mZo413br6rrJY

[@InfoRanker]

I never knew they could be cleaned. I always just replaced them. Good to know.

[@AmreSupply]

Thanks for watching! Cleaning the thermocouple might not always help but its a simple thing that you can try. Alternatively you can check the threaded connection into the valve for any corrosion. Pretty much anything that will disrupt the electrical signal, or decrease the voltage can prevent the gas valve from opening.

[@viathomas6933]

very good!

[@AmreSupply]

Thank you!

[@ipfmcd]

Brilliant. Great vid. Thanks guys!

[@AmreSupply]

You're welcome Iain! We're glad you found the video helpful!

[@shenglihuang5200]

Excellent video. Thank you!

[@AmreSupply]

You're welcome! We're glad you found it helpful!

[@cainarnold1]

Thanks for the information and help

[@AmreSupply]

You're welcome Arnold! We're glad you found it helpful!

[@BBB-ly8ro]

Hey Vance. You sure know your beans about gas. Thanks

[@AmreSupply]

Thank you!

[@LLStacheLarry]

Mine is over 20 years old. The thermalcoupler is up and down how does that come out. Is there a screw to take both pilot and thermalcouple out?

[@AmreSupply]

Thanks for watching. In some models the thermocouple and pilot flame will be mounted together in a small bracket. In these cases you'll have to unscrew the assembly to lower both pieces. Other models the thermocouple will just unscrew and slide out individually.

[@liondoor4554]

Thank you 🙏 thank you 😊 thank you‼️

[@AmreSupply]

You're very welcome!!

[@Andreamom001]

Mine is back in a hole and has pipes on either side. I can barely get anything near it. Is there some specialized tool needed or am I supposed to disassemble the whole thing to get access?

[@AmreSupply]

Thanks for watching. Without seeing the whole setup it is difficult to say what is needed to access the thermocouple. In some cases you can remove a side panel to gain more access. In other caess repairs are not easily done and won't have the same sort of ease of access.

[@INTERNA9]

THANX

[@AmreSupply]

You're welcome!

[@bahiatyree21]

I broke off the nut on the thermocouple.. Can i ask you can fix it or do i have to replace the whole hot water tank.

[@AmreSupply]

Thanks for watching. We have a video showing how to access and replace the thermocouple in a water heater. In many cases it is relatively simple to install a new thermocouple: kzbin.info/www/bejne/g6mZo413br6rrJY

[@c.rutherford]

I have acquired a house with an old late 50's Luxaire and no money to replace it. When lighting the pilot light, the flame is actually burning the thermocouple, and it glows. Is this safe? Maybe the pilot light is set too high? The pilot flame is quite large and forked. It just looks odd. Thank you.

[@AmreSupply]

Thanks for watching. Its likely that there is a lot of carbon that has built up on the pilot assembly that is messing with the pilot flame. This could change the size of the flame and where it is sitting on the thermocouple. Only the tip of the thermocouple should be in the flame, and it shouldn't be causing the thermocouple to glow red hot. You could try cleaning the pilot assembly, but if this is a new acquisition, then it might be worth getting it inspected by an HVAC tech.

[@c.rutherford]

@@AmreSupply Well one can spend money endlessly of course. I have already had the gas company check the furnace, and also paid a private HVAC company to come out and verify it had no leaks. Must I pay someone else to come out and let me know if there is too much carbon on the coupler? I'm becoming a fan of electric heaters.... given all the checking and dangers it seems far less expensive in the long run

[@AmreSupply]

@@c.rutherford Well in the meant time its worth cleaning the pilot assembly as well as the burners. If you do install a new furnace there are pros and cons to both gas and electric. Electric does have a simplicity to it, you are right about that.

[@Baloong]

So, I have replaced my thermocouple as it was dirty and I start it up(starts good) but after a few hours the pilot light just dies and I have to light it again. What could be the possible problem?

[@AmreSupply]

Thanks for watching. There's a few things you can check. Check to see if there is any corrosion between the thermocouple and the gas valve. Clean any calcium or anything that might reduce the voltage. The next thing to consider is the airflow. Standing pilot furnaces use atmospheric pressure to get rid of the exhaust. There should be a good supply of fresh air into the furnace room. As well dirty burners or a blockage in the vent can starve the system for air. A backdraft can prevent the pilot from staying lit.

[@partshnc]

The well-organized video not only demonstrates the replacement process but also provides a thorough explanation of a thermocouple's role in a furnace’s efficient operation. For quality thermocouple and other furnace spare parts, visit us.

[@AmreSupply]

Thanks for watching. All the parts shown in the video can be bought online at amresupply.com or in store at one the 12 AMRE locations.

[@anhocvoitumay1652]

Is the thermocouple for the attic furnace the same as for the water heater? Is there one specifically for the attic furnace? Thank you.

[@AmreSupply]

Thanks for watching. Most thermocouples are very similar with the only difference being the lenght. if the gas valve is similar then the thermocouples will be the same.

[@greenyouyo5870]

thank you so much for the video. question: cleaned the thermocouple, installed, however, the pilot only keep for about 5 minutes, then the furnace shut off, repeated 5 times all the same. shall I replace to a new thermocouple, or something else failed?

[@AmreSupply]

Hi Green Youyo, its likely that the thermocouple is starting to fail so its best to replace the thermocouple.

[@Sh.C.R.F]

Why is it not screwing back in? If the threading is stripped, what do I do? Thanks!

[@AmreSupply]

Thanks for watching. If the threads are stripped you might need to install a new pilot assembly / mount as that will have new threads.

[@mtnmosin2740]

Does it hurt the thermocouple if the tube gets squished or is it merely a heat conductor?

[@AmreSupply]

Thanks for watching. The thermocouple has an insulated wire inside the copper tube which both carries electrical signal created when it heats up. If the tube gets squished its possible that the wire inside might get damaged.

[@tqt4ya]

What would happen if there was a wire in the middle of those flames? The hvac repair person was here today and he stepped out to use the bathroom and i saw that one of those wires was inside of flame (it was red hot) and When I asked him about it he said that it was a sensor to make sure that the heater was working ... this video shows the sensor in a different place (not directly into the flame) I came to look it up because it looked like a fire hazard.

[@AmreSupply]

Thanks for watching. Is your furnace a standing pilot furnace or a direct ignition furnace? If it is a direct ignition furnace then it will have a draft inducer motor, a hot surface ignitor and it will also use a flame rod instead of a thermocouple. This detects the flame from the main burner. You can learn more in this video: kzbin.info/www/bejne/qoevpX2tnt1glZo As well we have many more furnace repair videos in this playlist: kzbin.info/aero/PLCo9SMjkdWBzorzNrARLKALj9fW7HzHMh

[@Kurt-ye4bw]

Does the thermocoupler have to be at a certain place

[@AmreSupply]

Thanks for watching. The thermocouple tip must sit inside of the pilot flame for it to work correctly.

[@brianwatson4183]

My old furnace cycles on and off, no flame sensor to clean. Could it be the T.C.

[@AmreSupply]

Thanks for watching. If you have a standing pilot furnace (and the pilot stays lit) but the furnace cycles on and off more than it should then it's likely a problem with one of the fan limit switches. These sorts of furnaces don't have an intelligent control board. The limit switches are used to help control how long the furnace and blower fan run. Though you might have more than one limit switch and the switch might look different, this replacement is shown in this video: kzbin.info/www/bejne/ZqfEkKqsrMt2eKM

[@zakikhan814]

if my pilot light wont ignite at all, then cud this be a dirty/bad thermocouple?

[@AmreSupply]

Thanks for watching. If the pilot won't light at all then its potentially an issue with the gas supply, the gas valve or a dirty pilot orifice.

[@dianebeland3290]

I have and old wall mounted heater in my basement. The thermocouple just sits curled up under the heater. I am never quite sure if that is the best place for it to work efficiently. I do not have a thermostat to control the temp.

[@AmreSupply]

Hi Diane, thank you for watching. Generally the thermocouple is positioned in the pilot flame or the heater will not work properly. If you don't have a thermostat, is the wall heater just control via a on-off switch?

[@bdoft9252]

nice video. question: have a (non electric) preway svp35r natural gas space heater in a cold sunroom. the thermostat setting on it at lowest number will still keep room heated to 65 degrees. Is there a way to chage the thermostat on it so that there is an 'off' position which does not turn off the pilot light? thanks.

[@AmreSupply]

Thanks for watching. I am not familiar with that particular space heater. Does the pilot stay lit as the unit cycles on and off at the low heat setting?

[@drewcagno]

How much do I tighten it in?

[@AmreSupply]

Thanks for watching. In this case it doesn't need to be extremely tight. Hand tight plus an extra quarter turn should be good.

[@Benthehitman32]

How do I remove the panel to get to the thermocouple?

[@AmreSupply]

Thanks for watching. If you're referring to the outer cover panel, it might have several screws on the side and will likely lift up slightly before you can pull it completely off. As well in some models there might be a smaller panel near the burner.

[@Benthehitman32]

@@AmreSupply Anyway I could email a picture of what I'm talking about?

[@AmreSupply]

@@Benthehitman32 There is no ability to attach pictures directly through email comments but we do have a email for our Customer Care Centre: [e-mail] if you add a note that the question is from KZbin then it will get forwarded to the right place.

[@Benthehitman32]

@@AmreSupply Alright I just emailed the customer service.

[@ssnydo3]

Aren't pilot lights generally always on? Therefore, wouldn't the thermocouple always detect the heat and create the voltage to allow gas to flow at all times?

[@AmreSupply]

Hi Sean, that is an excellent question! You are right that the pilot light stays on so that the furnace is ready to ignite the burners at any point. The gas valve has 2 solenoid valves in it. The first valve is controlled by the thermocouple and is placed before the gas valve that supplies the burners. The gas valve that supplies the burners is wired differently will only open when the furnace begins a heat cycle. Both valves are in-line so this means that when the thermocouple cools down it will shut of all gas to the pilot and the burners.

[@ssnydo3]

@@AmreSupply Thanks for the quick response. Can't say I follow. Does AMRE have a video explaining this? Thanks!

[@AmreSupply]

@@ssnydo3 You're welcome, we're just happy to help. We have some videos on standing pilot water heaters but it doesn't really describe the internal working of the gas valve any more than this video. This image does show it pretty clearly though, and you can see how the bypass button allows gas into the pilot: www.uniquevanities.com/bathroom-vanity-blog/wp-content/uploads/2011/10/pilot-light.jpg Keep in mind this image is slightly different than the furnace as it shows a main gas valve that is opened by manually by turning, rather than a solenoid controlled main gas valve. Still it shows how the thermocouple controls the gas before it even gets to the main gas valve.

[@monm309]

I'm having issues with mine. When it's turning on a loud bang happens, louder the usual, it sounds like if the gas was going and there is a delay on the fume.. any suggestions!?

[@AmreSupply]

Thank you for watching. It can be helpful to clean the burners and check if there is anything restricting airflow on the exhaust vent. If the exhaust vent is restricted in any way ( debris, leaves or snow on the vent cap) it can create static pressure and delay ignition.

[@chiraldude]

No No No!!! When a thermcouple stops working, it's usually not because the part in the flame is dirty, it is because the other end is not making good contact with the gas valve. Furnaces are often in damp basements and this moisture can often cause corrosion at the point where the thermocouple connects to the gas valve. Pull it out of the gas valve and gently rub the end with emery cloth. Wipe off with alcohol then insert an alcohol soaked Q-tip in the hole where it connects to the gas valve to clean the inner contact as well. This fixes 99% of thermocouple issues.

[@AmreSupply]

Hi Brian, thank you for sharing those are good tips. You are right that in some cases corrosion can make for a bad connection which can reduce the thermocouple voltage.

[@thealaskanbyrds]

Thank you both, working to get my heat going this am, its 53 in the house and -1 outside!

[@LuisNava01]

Is a good class Brian thanks

[@prettyboss275]

Do u have to do anything special before u pull it out

[@whiskerbiscuit99]

​@@AmreSupplythere is no voltage involved on this kind of thermocouple

[@wam44]

My furnace will short cycle after it runs. When it stops after a normal cycle it will turn on again for about 3 or 4 seconds and then shut down again until then next normal cycle. Is this due to thermocouple?

[@AmreSupply]

Thanks for watching. It depends on the type of furnace. If you have an intermittent pilot furnace then a bad thermocouple could cause it to cycle. If you have a newer furnace that uses a hot surface ignitor and flame sensor, then it work a little differently. You can learn more about short cycling in this video: kzbin.info/www/bejne/mGHWcnqqYpahn7c

[@wam44]

@@AmreSupply It is an ancient furnace - at least 30 years old. Planning in replacing soon but would like to solve this in the short term. I don't think it is an intermittent pilot because it stays lit all the time. I'll watch the vid you sent-Thanks!

[@wam44]

@@AmreSupply I watched that other vid-My furnace runs on a normal cycle but after it shuts down, it will turn on for 3 or 4 seconds then shut off and remain off until the next cycle begins. The scenarios in the other vid do not describe what my furnace is doing-thanks though...

[@AmreSupply]

@@wam44 If it is an older furnace, then it could be an issue with one of the fan limit switches. Without an intelligent control board the fan limit switches help control the timing of the blower fan as well as disconnect power to some of the circuits.

[@wam44]

@@AmreSupply Thanks again-From your comment and what I am reading the furnace's behavior appears related to the furnace needing to dissipate heat after running through a cycle. If the furnace is too hot after a cycle it will run the fan to cool itself off...I opened up the furnace - the jets look good-burning blue at least :-)-there is white flaky stuff that is present around the jets and some other areas. I will vacuum out. It was 3 months since last filter change so I changed it. It wasn't that dirty really. It seems to be cycling on less frequently now. Furnace is from 1983-maybe time to upgrade :-)

[@christopherrobin462]

I have a natural gas wall heater with thermostat and it will not turn down even on pilot full gas high at all time so it on or off only any ideas

[@AmreSupply]

Hi Cj, thanks for watching. There are a few things that could be causing your natural gas wall heater to run constantly and not shut off. It could be a bad thermostat, a bad gas valve or a shorted thermostat. If you disconnect one wire to the thermostat and the heater shuts off then you know that the thermostat was bad, that would be the first place to start.

[@rockks176]

Maybe i didn't hold the bypass long enough mine won't stay lit

[@AmreSupply]

Thank you for watching. If the pilot still won't stay lit even after letting the thermocouple heat up then there could be some corrosion where the thermocouple screws into the gas valve. Any corrosion can affect the voltage. You can clean this by unscrewing the thermocouple and cleaning both the thermocouple connection and the gas valve threads with some isopropyl alcohol and with a q-trip.

[@pioneer7777777]

Does any company make a thermocouple that won't constantly break? Getting so tired of going through there things every year.

[@AmreSupply]

Thanks for watching. Thermocouples are pretty similar between manufactures, so there won't be much difference. If you're finding that your thermocouples aren't lasting very long then its possible that the thermocouple is being heated past the normal operating range. This could be because of the position in the pilot flame, or the amount of gas that the pilot is burning. This can be adjusted but is not exactly a DIY job.

[@babalupicapau]

What if the pilot doesn’t click

[@AmreSupply]

Thanks for watching. Can you elaborate? Do you mean that the pilot doesn't click when pressing the bypass button?

[@IvankaB-ft6hd]

and how about if the burners are going but the fan will not start unless I put the fan on ON position instead of AUTO? the burners are working for a little while and then they shut off. Luckily we have electric heater so we will be fine till Monday. hmmmm

[@AmreSupply]

Hi Ivanka, thank you for watching. It sounds like it could be a problem with your limit switch. That is described in the last half of this video which is a video on why furnaces start and stop. It is focused more on forced draft furnaces though not standing pilot. kzbin.info/www/bejne/mGHWcnqqYpahn7c If your furnace is a standing pilot furnace then you likely have a "Fan limit switch". www.amresupply.com/catalog/Fan-Limit-Controls-HZ3D The fan limit switch will detect when the burners are at the right temperature and turn on the blower fan, as well as shut the blower fan off at the high temperatures. (This is different than a high limit switch in automatic furnaces, which only shut off at high temperatures.) All limit switches can fail or wear out overtime causing the blower fan to have issues running.

[@IvankaB-ft6hd]

@@AmreSupply I will look into it. Thank you so much. Was hoping for faulty thermostat but after getting new one and replacing it the furnace does the same thing. Burners going but fan will not start unless manual switch to ON. Will try to locate the switch now. Thank again

[@AmreSupply]

@@IvankaB-ft6hd You're welcome Ivanka. Best of luck to you.

[@LivraisonVIP-fn2mz]

hi whay my furnace cutoff after 10 mn working (trane v90)

[@AmreSupply]

Thanks for watching. If the furnace cuts off after 10 minutes then it could be a faulty limit switch.

[@ballinblaza]

mine doesnt have that tube that leads to the pilot

[@AmreSupply]

Thanks for watching. Are you still able to locate the pilot assembly and thermocouple? There are some models that use thermopiles which are a little different.

[@PostUp_Time]

*what actually happens to a thermocouple to go bad? seems like not anything there to go bad*

[@AmreSupply]

Thank you for watching. Corrosion can effect the thermocouple and the connections. As well over time metal fatigue can cause the thermocouple to fail.

[@14dogday]

almost make's me wanna be a furnace man

[@AmreSupply]

Thanks for watching! HVAC is a fascinating field. We have many more videos if you are curious on learning more: kzbin.info/www/bejne/qoevpX2tnt1glZo

[@babyscorner2023]

im so screwed! my man just passed away, and ive outlived everybody! i have nobody to ask for help..im a double leg amputee and trying to learn to take care of EVERYTHING on my own...i ABSOLUTELY can NOT find ANY button to hold down! my hot water heater blew out about 3 wks ago, and i went to turn on my heat last week, and nothing happened!..uhhhg!! ive been starring at the furnace for days, i can not find any red button,or any button to hold down. AND i can not even see where the damn pilot even is!! im usually very quick to catch on to this kind of stuff. but i my furnace looks diff compared to all the vids of been watching..

[@AmreSupply]

Hi Cynthia, thank you for watching. It can be difficult as there is a bit of variation between models. If there is no bypass button but you still are certain that your furnace has a pilot light then you might have a intermittent pilot which is an automatic lighting of the pilot when heating is needed. If you don't have a pilot light then you might have a furnace that uses hot surface ignition. You can learn more about this here: kzbin.info/www/bejne/qoevpX2tnt1glZo

[@babyscorner2023]

@@AmreSupply thank you for your time!..but OH BOY! i think im in trouble, ive done everything ive been watching, but im not certain of anything!,.i feel like a dingbat! all ive managed to do is get it to blow cold air, when i bought the house it had central air, but day before move in, somebody swiped the unit outside, so ive never used it. and in 14 yrs, ive never had to do anything accept turn up the thermostat in the fall. BUT 5 yrs ago a bird got in chimney and died, causing an issue with,i believe a "fan motor" a neighbor knew how, and replaced it and ive been good to go since. but a few weeks ago i went to kick up the thermostat and nothing happened. of course i started getting people telling me i probly had to light the pilot. of course nobody had the time to actually how me how, im 54 now and ill, the cold is not my friend at all!,.lol...niether is money..so getting somebody in here to help, is going to be rough. weve already had temps in the 30's! so ive been breaking out all my blankets...bout the only thing i can think of is posting a vid of what my furnace looks like. but ive got that sick pit in my stomach thats telling me im in real trouble..im already in trouble with my water heater,it blew out all over my basement almost a month ago. my issues always come in bundles!,.uhg!!

[@AmreSupply]

​@@babyscorner2023 Thanks for the update. The other thing you can do is look for your furnace manual. It will tell you the type of furnace and will have instructions for lighting the pilot if it is a standing pilot furnace: the instructions for lighting the pilot can be seen more specifically in this video: kzbin.info/www/bejne/aXqohJtnZ6aErZY Additionally you can use the model number of your furnace and do an internet search. This can often bring up the details of what type of furnace it is. Also look closely at the gas valve, if there is no button then it could be an intermittent pilot or a hot surface ignition furnace. If the furnace has a hot surface ignitor then, a faulty ignitor can prevent the furnace from igniting. If it is a intermittent pilot furnace then it could be a faulty spark ignitor. If its not starting at all you can try to follow these steps: kzbin.info/www/bejne/eJqaZ6Rmid-ijZo If you are unsure then the best course of action is to call an HVAC technician to take a look.

[@frankjones6406]

No pilot position for me

[@AmreSupply]

Thanks for watching. It might be worth checking your furnace manual. You might have a intermittent pilot which will automatically light the pilot when heating is needed. These function a little differently than manual pilot furnaces. Unfortunately we don't have in-depth troubleshooting for intermittent pilot furnaces but if it has a thermocouple then it can still be replaced as per the steps of this video.

[@jerickhenry]

Buderus logano G115

[@AmreSupply]

Thanks for watching.

[@stephenbierlein2517]

You've must've never done service. It cheaper to change than have a call back.

[@AmreSupply]

Hi Stephan, thanks for watching. You are right that it is often best to install a new thermocouple. This video is meant to inform and many homeowners will likely use this as a guide so for them, they would be taking an initial look at it first before getting the part.

[@termisium3706]

Cleaning works guys always clean first. Use alcohol to clean better.

[@AmreSupply]

Yes you are right that cleaning with a bit of alcohol works great.

[@truth1267]

My furnace still won't stay lit

[@AmreSupply]

Thanks for watching. If you have a multimeter you can test the thermocouple if it's producing enough voltage (the steps are the same to test as a water heater). You can do this even if you've recently replaced the thermocouple. kzbin.info/www/bejne/gqaYeKmYq9ijg9k If the new thermocouple isn't producing enough voltage, then it might not be sitting in the flame correctly, or the pilot flame might be weak. Cleaning the pilot assembly can help. If the thermocouple produces enough voltage in the direct test, then its worth cleaning the connection between the thermocouple and the gas valve. The threads that the gas valve screws into can become corroded. Corrosion can restrict the flow of electricity from the thermocouple. Using alcohol and a q-tip you can clean the threads. Hope this helps!

[@allengrate4242]

I can't keep the tip of the thermocouple locked into position. It's either too high and hits one of the main burners. Or too low and is't exposed enough. After installation it's always lose. What am I doing wrong?

[@AmreSupply]

Hi Allen, thank you for watching. Often there's a sleeve, small ring or a push fit connector that is needed to help keep the thermocouple in place. 4:30 shows these connectors. Did your old thermocouple have one of those on it?

[@allengrate4242]

yes it has a 'bayonet' type retainer, so I think I simply have the incorrect sequencing of parts...? In either case I did finally get it to stay in position, however - no joy. Pilot still w/n ignite. I have a good gas supply because my fireplace works fine. Which branches off just prior to the furnace feed. So the next component is the gas valve itself. ????

[@AmreSupply]

​@@allengrate4242 The thermocouple will prevent the pilot from staying lit, but if the pilot isn't lighting at all, that is separate from the thermocouple. To light the pilot you need gas, a spark (or flame) and proper airflow. Pressing the down the pilot (bypass) button while lighting is manually opening the gas valve, letting gas flow through the pilot tube (all the thermocouple does is keep open the gas valve after you stop pressing the bypass, but you need a flame first). First check the pilot tube, and make sure its not bent or kinked as any restriction in the pilot gas supply will prevent the pilot from lighting at all. As well the pilot orifice can sometimes buildup with carbon, and can become plugged. A small wire can be used to help clean the orifice. If you still don't have a flame , then its likely that there's no gas being sent to the pilot orifice, so it could be a problem with the gas valve not opening.

[@justinperry68]

My god, if you have a furnace this old, purchase a new one, and quit throwing money away

[@AmreSupply]

Thanks for watching. A thermocouple only costs 10 - 20 dollars, and for some people that can get their furnace running again. Not everyone has the money for a new furnace in these difficult times so these small repairs are essential for many people.

[@madmax8620]

HELP! I really hope you are still available to answer questions, because we are freezing! SO , my main gas valve is often failing to open, Im pretty sure we have a intermittent pilot ignitor because of the small gas tube from it and the electric tazer starter that lights it... so that first small flame will light, but recently, the main valve/ tubes won't light up, and it is short cycling when they do eventually light. It was very hard to reach, but I tried to clean what I think was the Flame Sensor rod, with the dollar bill and wire brush, which did NOT fix this. Is there Both a flame sensor AND a thermal couple in this furnace? its really hard to see in there. Or is it just one or the other, that furnaces have?? I had a lot of water in the garage too recently when this soon started, from a broken water pipe in another part of the garge, and hard to dry out since the winter time, so maybe it has corrosion?? Thank you so much for your time and reply!!!

[@AmreSupply]

Thanks for watching. The model in this video did not have a control board capablle of showing codes, so it just had a pilot light and thermocouple. It is unlikely for a model to have both a thermocouple and flame sensor. If your model has a flame sensor then the control board will monitor the flame sensor to see if an electrical path is completed through the flames, through the metal of the burner to ground. So cleaning the burners can help in these cases. You can see more in this video: kzbin.infoBl2hGox1lcs

[@madmax8620]

@AmreSupply wow, thanks so much for responding! I watched your linked vid short... but mine is not a High Efficiency furnace. Which ever sensor it was that I cleaned, definitely had a singular regular red wire going to the board. Ok, So then it was a flame sensor and not a coupler... You say in the short vid linked, that it could be a "dirty?" Heat Exchanger causing the gas to not flow... so im worried if a CRACKED exchanger could cause my intermittent gas delivery and short cycling condition?? I hope not, because we dont have money for anything like that, and we aren't sure if this mean we are being Carbon Monoxide poisoned or not from this issue?! This furnace also does not have a code light, or even a door safety switch or its own power off switch. Its a Janitrol 1989 is on its inside lable, and first four of ser# is 9104... Me and 2 other handymen homerepair guys i asked, could NEVER figure out WHERE THE FILTER IS AT. I asked the previous long time owner, and they said they didn't know either or ever had it changed possibly. The is a lable inside too that reads "filter behind blower inside compartment" which seems crazy difficult to access and open with many bolts and misc parts in the way. Thank you so much. And sorry I was perhaps too detailed and long in trying to share anything relevant that might give us warmth again...or not kill us in our sleep(this is a rental and no detectors in the home,)

[@AmreSupply]

@@madmax8620 The best thing to do is to go out and get a Carbon Monoxide Detector. In most cases place the CO detector 5 - 15 feet away from the furnace. Check your local building codes or laws for the exact details but your landlord should be responsible for making sure that CO detectors are installed in any space that has a gas appliance or furnace. If the CO detector goes off, then leave premises and call a technician. Next check your rental agreement and figure out who exactly is responsible for any furnace repairs. A cracked heat exchanger or major issues with a furnace caused by long-term normal use, is generally the landlords responsibility.

[@madmax8620]

@AmreSupply thank you for that concern, but in my particular situation, I am on my own with this, the landlord is AWOL. Otherwise, I would make them responsible. And so that is why I am trying to figure it out with any help I can find... So the furnace is in the garage, so placing Monoxide alarms there would go UNheard. But my main question was, Could a cracked/damaged heat exchanger be the cause, or most likely reason, for the issue of the gas valve intermittently functioning, or more likely the dirty tubes or bad sensor like you first mentioned? I have no clue if its cracked, I just was throwing out worst case scenario, if it applies to this... im just learning about it all.

[@AmreSupply]

​@@madmax8620 Before assuming a cracked heat exchanger (which can be difficult to determine), first check to make sure that there are no restrictions to the exhaust vent on the exterior of the home. Make sure that there is a good air supply. Clean the burners and the flame sensor. Generally a sensor problem will mean that the furnace lights, and shuts off shortly after. If the burners don't light, then its likely an issue with the gas valve not opening. There could also be low gas pressure, but just enough for the pilot.

[@LeonardHoldman]

M.

[@AmreSupply]

Thanks for watching.

[@rsanchez7111]

Thank you Sir..

[@AmreSupply]

You're welcome!

[@JackieGreeneBeauty]

Thank you!

[@AmreSupply]

You're welcome Jackie!