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Furnace Pilot Light Goes Off Sometimes, Any Help Appreciated

Discussion in 'Do It Yourself (Not Computer-Related)' started by mrairbrush, Jan 21, 2008.

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  1. mrairbrush

    mrairbrush Thread Starter

    Jan 21, 2008
    I am new to this forum
    I hope to contact a technician that can tell me what I might do to fix this problem.
    Here is the problem if I may.

    We bought this house approx 1 year ago. The furnace is over 16 years old.
    Just yesterday the problem began. The furnace was blowing cold air. I checked and the pilot light was out. It is not electronic , it must be lit at all times. I folowed the book instructions and turned thermostat off and turned the gas button to the off position for 5 minutes. Then I turned it to pilot position and pushed down the red button to light the pilot.
    I held for a moment and it stayed lit. I then turned it to on position
    We set the thermostat and it lit perfectly and ran great.
    It is cold here today it is Jan 21st ,2008 . The furnace ran good for about two hours on and off. Then again we have cold air , so I look and of course pilot is off again.
    I do the same thing. This happened two times yesterday eve.
    Then the thing ran all night and is running fine now and staying lit.

    It seems to periodically go out for some un known reason.

    Could this be a pilot issue that I need to replace it ?
    Or is this a thrmoal coupling issue ?
    Can anyone help me ?

    Funds are down right now due to Holiday spending. Of course it didnt happen when I had a few bucks to fix it. It had to happen on just about the coldest day we have had this season.
    If your a tech and have a possible solution I would be glad to read it
    Thanks again
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  3. iltos


    Jun 13, 2004
    welcome to TSG, mrairbrush

    a unit that old, it's probably the thermocouple....they respond to the temperatue of the pilot flame and either open or close the gas to the burners, depending on their reading

    when they are worn out, (due, probably in your case, to it being in the flame of the pilot for 16 years), they can stop working....public utility companies use to replace them for free....that may not be true anymore.
  4. mrairbrush

    mrairbrush Thread Starter

    Jan 21, 2008
    thank you for your quick response.
    I was told that cleaning out ( blowing out pilot with air after removing it could fix the problem if dirt or dust got in it)

    I think your answer makes more sense
    It has worked good now for the last 15 hours
    comes on and off and heats the house

    I am thinking that coupling is getting bad.
    Maybe I will just replace both pilot and thermal coupling .
    Then may just replace the whole furnace this coming summer

    thanks again
  5. cwwozniak

    cwwozniak Chuck Trusted Advisor

    Nov 28, 2005
    We also have an old house with an old gas fired furnace with a gas pilot light. We have an annual service contract with a local HVAC company that includes yearly inspection and maintenance. Every fall they clean the pilot light and burner as well as replace the thermocouple. The tech said is cheaper for them to just replace it than to have to come back on a service call in case the old fails in the middle of the night.

    DISCLAIMER: I am not an HVAC technician. I am only describing my own personal experience and what has worked for me in the past. There is not guarantee that it will work for you in similar or safe manner.

    I have found that a few months after the service call and when we have a really cold temperatures for a while, that the pilot light goes out. The furnace is in a small room next to the crawl space. When outside temperatures drop below about +15F, we usually crack open the access door between the furnace room and the crawl space (Don't want frozen pipes). I am not sure if the lower temperature in the furnace room is the problem or if the convection flow of the air in the room is enough to blow out or deflect the pilot light flame from the thermocouple.

    The first time this happened, I relit the pilot light and noticed that flame from the pilot light was not fully hitting the thermocouple and the thermocouple had a bit of white soot on in it. I turned off the pilot light and gave everything a few minutes to cool off. I then used some fine emery cloth to clean the slot in the pilot light and the surface of the thermocouple. I lit the pilot light and noticed that the flame hitting the thermocouple was a bit wider. The furnace worked fine for the rest of the winter.
  6. mrairbrush

    mrairbrush Thread Starter

    Jan 21, 2008
    Thank You CW
    My furnace is in our basement
    I did notice that their is some white coloring on the thermal coupling
    So. I think I will try what you said.
    I will clean it up good and see if that does it
    If not
    I may just replace the coupling and pilot.

    I was just commenting to my family that we let this pilot burn all summer
    I think from now on I will turn it all off for summer and shut the hole thing off

    May just replace the whole furnace this summer or since we want to move to the country I may just fix it and sell the house. Of course making sure the furnace is working good beforehand. New coupling , new pilot and thourough inspection

    Thanks again
  7. Knotbored


    Jun 5, 2004
    I just checked Google and found many Honeywell Thermocouple listings for $4 to $5 dollars.
    I believe it would be worth the time and effort to just replace it rather then cleaning it and perhaps overlooking some other problem.
    A neighbor had a pilot problem with wind blowing it out because exhaust was too short, cured with a 2 foot exhaust extention, but that was on a new manuf home, not an established house.
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