Posted on 34 Comments

Problem: FYI Troubleshooting and cleaning a Bryant Carrier 3 wire pilot burner.

This customer was kind enough to share with me how he repaired his Bryant Carrier 3 Wire pilot burner. This customer had installed a new 3 wire pilot burner, then decided to clean the old 3 wire pilot burner to see if he could get it working. Sure enough he got it working again after 20 years of service! Below we have two YouTube videos made by Grayfurnaceman which show how to troubleshoot and the operation of a 3 wire pilot burner. Thanks Grayfurnaceman for making this informative video. We sell the Bryant Carrier 3 wire pilot assembly on the following page:  If you have any questions please feel free to email us at: or comment in the comments section below. We would love to have your business!

3 wire pilot burner all

FYI – Without making any adjustments to the Gas Flow, I noticed on the new 3 wire pilot burner, that more of the pilot flame appeared to be striking the switch plate when the blower kicked in. So I re-installed it after performing the below maintenance and it too worked again. However, I figured 20 years of service was good enough and retired the old one with the new one.
a) From inside the chamber where the gas would enter the Pilot Burner and the brass fitting screws in, I blew out the Gas Nozzle and the little cone nipple that the compression fitting sits into. The hole on the cone looked a little stopped up.
b) Took Sand Paper to the strike plate and wet sanded it back to bare metal again.
It looked like the blower kicking in was stealing enough of the pilot flame away from the strike plate to cause it to cut in and out.
Thanks again for your attention and service.
Much appreciated.
Below we have two YouTube videos made by Grayfurnaceman which shows the operation and troubleshooting of a 3 wire pilot burner. Thanks Grayfurnaceman for making this informative video.

34 thoughts on “Problem: FYI Troubleshooting and cleaning a Bryant Carrier 3 wire pilot burner.

  1. Have a Payne furnace model 395baw024040 having problems with the pilot staying lit, I replaced the 3 wire pilot assembly, and still did not fix the problem, the pilot will light and then shut off, relight and shut off, it’s as if the gas is shutting off .. could this be the gas valve or the igniter? Any help would be appreciated

    1. Hi Michael! I would like to suggest that you test the PV (pilot valve) on your gas valve. Your gas valve should have an MV (main valve solenoid) and a PV (pilot valve solenoid) You should be getting a constant 24 to 28 volts AC to the PV when the pilot is trying to lite. If the voltage is going away from the PV during the furnace lighting cycle then you have a control board problem or a problem with the device that is supplying power to the gas valve. If you are getting a constant 24 volts to the PV and the gas is going out then this would mean you need a new gas valve. These 3 wire pilots can be hard to troublshoot. I hope you can easily find and fix the problem. Steve

      1. I have the exact same furnace as Michael, with the exact same issue. The pilot lights stays on for a bit then goes out and the igniter keeps trying to keep it lit. The burners never light. The gas valve is model SX345NSX-12, and don’t really understand your troubleshooting for the valve.

      2. Hi Kevin! You will need a voltmeter to troubleshoot your problem. You would need to test the PV (pilot valve) on your gas valve to see if you are getting a constant 24 volts to the PV of the gas valve when the pilot gas is going out. If you are getting a constant 24 volts to PV and the gas valve is not sending gas to the 3 wire pilot then you have a gas valve problem. If you are not getting a constant 24 volts to the PV of the gas valve then you probably have a 3 wire pilot problem or a control board problem. I would like to suggest that you try cleaning the 3-wire pilot with compressed air and make sure you are getting a good blue flame hitting the heat sensing plate on the 3 wire pilot burner. I hope you can easily find and fix the problem. Steve

      3. I know how to use a voltmeter and usually am pretty handy. But I don’t know which wires on the gas valve to test and have not been able to find any information about this valve.

      4. Hi Kevin! I do not really know what your gas valve looks like, but most of the older valves were marked on the top of the valve with a “PV” (pilot valve) and “MV” (main valve). You should be able to test the PV and MV with a voltmeter to see if the PV is getting 24 volts to keep the pilot burning and MV to keep the main burners burning. I am sorry, that I do not know that much about your pilot system other than it is really old and can be hard to troubleshoot. Sorry that I can not be of more help. Steve

      5. Fixed my problem, the inducer motor was not turning. Funny how I didn’t even notice that the fan inside the cabinet wasn’t spinning. I removed the inducer and got it spinning freely, reinstalled it and turned on the furnace. The burners lit and it’s working again!

      6. Great! Fantastic! Awesome! So glad to hear that you fixed your furnace by getting the inducer spinning again! Thanks so much for sharing this great news! Steve

  2. What a great thing to find the solution to my 33 year old Carrier 58GS-150-161JA ‘s start-up issue.
    The Pilot light came on, the burner started fully then shut down in seconds only to have the pilot igniter relight the pilot, then the burner only to start the cycle again and again…..
    I Cleaned the temperature sensor surface with a bit of scotch bright scouring pad; removed the pilot gas jet and cleared the orifice with a small sewing needle, problem solved. This after 4 trips by the service tech trying one thing and another including a new gas valve and the Gas Co confirming the delivery gas pressure was good at a cost of $210.
    Thank You so much for sharing the information in the video.

    1. Hi Mr. Bunker! Thanks so very much for your kind words and for letting us know the great news! I am very glad to hear that you were able to fix your furnace’s 3 wire pilot problem! Congratulations! Thanks so very much for taking your time to let us know how you fixed the problem. God bless you and your family today and always! Steve

  3. I have a similar old 58GS050 furnace. Just recently noticed that twice after the furnace was off for longer time (a couple hours), the pilot fail to get the main burner lit. It feels like the pilot was locked out, as if I reboot the system via Nest app, no sparking. After a few minutes, reboot, the pilot is on instantly, with solid blue strong fire, but the igniter seems to spark repeated still, until the main fire is on. Also it takes some good 30s to get the main fire lit with the pilot flame heating that “metal rod”(thermocouple?) and slowly turn it red. Where should I start about cleaning (or replacing?) Thanks in advance.

    1. Hi Ray! I would try cleaning the 3 wire pilot first by turning the furnace off, wearing some safety glasses and a mask, and then use compressed air to blow the 3 wire pilot and flame strike plate off. Make sure that when the pilot is lit that you have a strong blue flame hitting the heat sensing plate. If you are not getting a nice blue flame then you might try adjusting the pilot flame on the gas valve or you may have to take the 3 wire pilot apart and clean the tiny hole that allows the gas to go up to the pilot. Sometimes the orifice will get partially stopped up with white junk. If you do not want to do that then I would recommend trying to see if a replacement solves the problem. We sell a replacement on the following page: I have heard cases where the Nest thermostats rob power from the furnace. I would suggest making sure that you are getting a good solid 24 to 28 volts AC between the R and C terminals on your control board when the pilot is trying to light. If you are not getting a minimum of 24 volts then you might need to get a higher VA transformer. Most transformers are 40 VA you might need to replace your transformer with a 50 VA or higher transformer to satisfy the needs of the Nest thermostat. Steve

  4. I have been through so many of these 3 wire pilot assemblies I lost track.

    This past November 2020 I received a new one FLS0005 and it worked but lasted only about 1 month until it started making my 6 burners explode on ignition.

    Replaced it with a LH680005 pilot which worked but kept ticking through the entire heating cycle.

    On Dec 20, 2020, I installed a new LH680005 and it worked until January 10, 2021. Took it out because it like the first one was making my 6 burners explode when the main gas was first opened. This is a very scary thing to have happening in your home with your family inside.

    Today is January 10, 2021, and I just installed a brand new FLS0005 pilot assembly which took care of the exploding problem.

    My question is why are so many of these pilot assemblies inherently so unreliable? Both manufacturers brand new pilots last from 2 to 4 weeks and then start making your gas furnace explode loudly.

    I have replaced many of these assemblies so know how they look and work inside.

    I just think that the warp switch in both manufacturers pilots just are not designed for the heat and warp out of shape in a very short time such that the main burner contact is turned on too rapidly for full flow before the pilot flame has any chance to ignite.

    It you have a unit which ticks that means that the first internal contact is not releasing when it should. Both the pilot and main burners are turned off and on by some springy copper metal and the second one of the other contact is not connecting and disconnecting perfectly anyone will have a problem with these 3 wire pilots!!

    1. Hi John! I have never heard of anyone having this much trouble with the 3 wire pilots. We have been selling the LH680005’s for many years without any know problems and the FLS0005 for two years without any know problems. I know these have been around for over 30 years and recently Bryant Carrier quit making them that is why we started selling the FLS0005. You might ask the manufacturer these questions because I have no idea why all of your 3 wire pilots have been failing on short notice! So very sorry to hear that you are having all these problems with the 3 wire pilots! So sorry that I can not give you any advice. Steve

    2. You may want to use OEM carrier pilot assy. I been at it over 35 years and I only use OEM on 3 wire pilot. Never had any problems. Good luck in future.

      1. Hi Robert! I heard that Bryant and Carrier quit making the OEM 3 wire pilot burners several years ago. If you know of a supplier who still has the OEM LH680005 in stock please let us know so I can purchase some. Thanks so very much for your comments. Steve

  5. I have a Bryant 398AAW furnace and would like to replace the the three wire pilot relite. I have LPG, does the replacement come with another orifice to accommodate LPG furnaces? Thank you.

    1. Hi Mark! No sir, the Supco FLS0005 3 wire pilot burner that we sell is set up for natural gas and does not come with the orifice to convert to LP gas. We sell the 3 wire pilot on the following page: You might be able to use the orifice out of your old 3 wire pilot, but I am not sure that you can do that. Steve

  6. I have had the same problems for years but even after cleaning the orfice and strike plate the only way it will ignite is if the electrode is right in front of the gas flow. It always lights if I put a fireplace lighter in there to start the flame so it must be getting enough gas. Would that mean that the spark is too weak? Both the hold and pick measure 26 VAC when the electrode is sparking. This is the stupidest and most unreliable design I have seen in 70 years!! Should I turn up the gas pressure on the pilot or replace the 990-195 spark box????

    1. Hi John!
      I am sorry that you wasted your time writing to me because I have had very little experience with repairing and troubleshooting the 3 wire pilot furnaces. Yes, I would suggest trying to turn up the amount of gas that is coming from the gas valve to the pilot. If that doesn’t work then I would try adjusting the distance the spark ignitor is from the ground on the pilot so that you have a longer spark distance. If that does not work then I would recommend a spark box as we sell on the following page: There are lots of information on troubleshooting the 3 wire system. This is what I found when I googled “troubleshooting the 3 wire pilot burner assembly” I am sorry that I can not be of more help because of my lack of knowledge with the 3 wire pilot burning system. Our Bryant Carrier, Day & Night parts program does not find the model number for your furnace. I am guessing since the furnace is too old. If you really want to keep the furnace and can not figure out what is wrong with the ignition system then you could install a new standing pilot gas valve with a thermocouple. Sorry that I can not help you out. Steve

  7. Have a 40 year old Day & Night furnace and the 3 wire pilot has basically been the only problem except for having to change the spark box once.

    Lately I have been having trouble with the 3 wire pilot in that it keeps sparking but will not ignite the gas. However I know the gas is coming through the pilot because it always lights up with a fireplace lighter. Seems they are very tempermental in that sometimes the electrode has to spark right in front of the gas tube to ignite the gas whereas other times it doesn’t.

    I have taken these switches apart and can see how they work off of two contacts. One for the pilot and one for the main burners. But by design i can also see why they are definitely NOT a reliable part.

    Never understand why sometimes the spark has to be right in front of the gas coming out the pilot tube and other times it does not.

    Have cleaned these units several times as far as the orfice and the strike plate but that really never seems to help.

    Would be nice to know if I need a stronger spark or not. How to tell if the spark i am getting is enough or not? I have no idea.

    Spark box is part number 990-195.

    Other than the 3 wire pilot real being a pain and unreliable the unit has held up for 40 years without any problems!!

    1. Glad to hear that your furnace has lasted over 40 years! That is remarkable! I am sorry, that I do not know how to measure the spark from the spark box to tell if the voltage is right or not. If you have not already cleaned the pilot then it sounds like you are not getting enough gas to the 3 wire pilot. You may need to take the pilot tube off that connects to the pilot and thoroughly clean the pilot with compressed air. The pilot has a very small pinhole up inside the pilot that has to be open I have had to use pins to reestablish the pinhole in some pilots if the compressed air does not work. Hopefully, if you get enough gas with a hot blue flame on the sensor plate the 3 wire pilot will start working again. If you want me to look up parts for your furnace then please send me your furnace’s product number to our email address: and I will try to look up the parts if the furnace is not too old.

  8. My 3 wire pilot use to light but pilot would blow out, so I cleaned it out even the burners and then try to light it. But it just sparked but i could light it with lighter but burners would never kick on. Now pilot will not light even with lighter, the igniter just keeps clicking unless i connect the black wire above that opens gas i believe its number 3 of 5 on wires into gas valve. Help is it igniter gas vavle and 3 wire pilot?

    1. Hi Michael! I am sorry, but I have the hardest time troubleshooting these 3 wire pilots. I remember than I replaced the control board, spark ignitor and the 3 wire pilot and the problem ended up being the gas valve! Sorry that I do not know much about how to troubleshoot these. I would think if you are not getting 24 volts to the gas valve PV (pilot valve) then you either have a control board problem or a 3 wire pilot problem. If you are getting 24 volts to PV and the gas valve is not opening then you would have a gas valve problem. Here is a link to a pretty good Youtube video on how the three-wire pilot system works: I hope this helps you figure out the problem. We do sell a 3 wire pilot on the following page: Sorry, but it would be a guess as to whether this is the actual problem with your furnace or not. So sorry that I can not be much help. Steve

  9. I have this part it continues to click but never lights the pilot. seems that it is just not getting the gas for the pilot to ignite. does this part controle the flow of gas to the pilot or is that up at the valve assembly?

    1. Hi Jay! The 3-wire pilot burner does not control the gas going to the pilot. The gas valve controls the gas going to the 3 wire pilot burner. There should be a PV (pilot valve) and an MV (main valve) on your gas valve. PV should have 24 volts going to it to light the pilot when your thermostat calls for heat. You should be getting 24 volts between W and C (com) from your thermostat to your control board then 24 volts to the PV on your gas valve. I would suggest that you make sure that the limit on the furnace is closed. Steve

      1. I have this issue with a 30 year old Payne 396J furnace- the spark looks good, and most of the time it lights the pilot, but sometimes it just sparks for extended periods- like hours- without lighting. I know gas is flowing through the pilot because if I try lighting the pilot with a lighter or even just blow on it the pilot lights and everything works fine. The spark looks strong to me, but maybe it is weak and I need a new ignitor? Or should I just replace the entire assembly?

      2. Hi Ron! It sounds like you are not getting enough gas to light the pilot. I would suggest that you turn the gas off to your furnace and take 3 wire pilot out and blow it out with compressed air. Take the pilot gas tube off and make sure that the tiny orifice inside the 3 wire pilot is not stopped up with white gas dust. The orifice on the pilots are really small and can get partially stopped up. Clean the pilot up, reinstall the pilot and hope that fixes it. If it does not you might check and see if the gas valve has an adjustment on the PV (pilot valve). You might try to open this up to supply more gas to the pilot. We do sell a new LH680005 by Supco on the following page: I hope you can get the problem fixed soon! Steve

      3. Steve, thanks so much for your reply. I think you are correct. When I took apart the pilot line the orifice fell out, along with dust and debris. After cleaning the pilot flame is noticeably larger. Hopefully this will fix the issue.

      4. Thanks, Ron! I hope the cleaning fixes your problem! Best of luck! Steve

  10. Wiring diagram please
    White Green Yellow.
    Commonly closed / open

    Can’t buy $100 replacement part.
    repair with my own skills (electronics) might save me $$

    1. Hi David! I am sorry we do not have wiring diagrams for furnaces. Your furnace should have a wiring diagram attached to the furnace blower door or some where on the furnace body. Sorry that I can not help you out with a wiring diagram. Steve

  11. Thank you! I had worked out that the switch wasn’t working, but the problem was blockage in the pilot tube. Cleaned that out and now the pilot light branches properly and the flame sensor switches correctly.

    1. Great! Fantastic! Glad to hear that you fixed your furnace by cleaning out a blockage in the pilot tube! Yes, the flame sensing plate on the 3 wire pilot must have a good strong blue flame or it will not work. Thanks so very much for letting me and others know that a dirty pilot tube could cause the 3 wire pilot not to work. Hope you have a great Christmas and a Happy New Year! Steve

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