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  1. #1
    Join Date
    Apr 2009
    Midlothian, Il.

    Default furnace cycling on and off

    Hello, I have a question if anyone can help me out. My thermostat is set at 68 and the temp. is 64. My igniter or glow plug gets hot and the furnace fires up. Then about 5 seconds later i see the plug cooling down and the gas shut down. I did the gas shut down on the back of the panel waited the 5 minutes etc. Thank You
    Last edited by walleye0000; 04-13-2009 at 04:59 PM.

  2. #2
    Join Date
    Jun 2007
    Fayette County, Ohio

    Default Re: furnace cycling on and off

    Either the flame is not going all the way across the unit or the flame sensor is bad. . Some times just cleaning the tip with some fine steel wool will cure the problem.
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  3. #3
    Join Date
    Aug 2007
    The Great White North

    Default Re: furnace cycling on and off

    Many things can cause the firing to shut down.....

    Thermal coupler
    negative pressure switch and/or hose
    blocked intake
    blocked exhaust
    poor electrical connections internally
    poor ground connection
    faulty module
    faulty blower motor
    faulty temp sensor

    so on ....
    "" an ounce of perception -- a pound of obscure "
    - Rush

  4. #4
    Join Date
    Jan 2009

    Default Re: furnace cycling on and off

    To add to the above posts, many times I find if you follow the igniter/probe wire back to the gas valve of control module, the connection is suspect, I've had to tie wrap them in a certain direction to get a good connection until I was able to replace the valve or module.


  5. #5
    Join Date
    Jul 2009

    Default Re: furnace cycling on and off

    If the furnace fires up and shuts down 5 seconds later it is more than likely the flame sensor, they are designed to shut the unit down after that amount of time if it doesn't see the flame, as JLM said. Good Luck!!!

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