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  1. #1
    Join Date
    Jan 2020
    Posts
    2
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    Limit switch error code but switch is working

    Hi everyone, appreciate all of the information Iíve gotten from the site in the past. Usually I can skim and find my answer but not this time.

    Iíve got a Coleman gas furnace model number G8C05012MUB12G thatís showing 4 blinking red lights. Limit switch error code.

    It will cycle normally, fire up ok but only for 20 seconds or so, then it shuts off and the 4 red lights flash 3 or 4 times then the furnace goes back to its normal resting state.

    I recently replaced the filters and they still look good. My ductwork hasnít changed since we bought it new in 2006.

    Iíve never used a multimeter before but I pulled up a video on YouTube that walked me through testing the limit switch and three rollout switches. I did that by cutting power, removing each switch one at a time, setting the multimeter dial at 20 k on the Ohm side and testing for resistance. All four switches read 0.00. I was really hoping one of them would have a reading.

    And I have always played hell finding Coleman manuals online. The idiots who built this house didnít put the furnace manual in the holder on the side of the unit (and THIS idiot didnít think to ask for it), so Iíve come about as far as I can come on my own.

    Really appreciate any help you can give me. Iím not gifted with this stuff but Iíve got a couple little ones double-layered in the living room so Iíll try my hand at anything. Thanks.

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    27,383
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    The limits doing its job. Call your service provider. Request a copy of the IOM.

  3. #3
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    4,434
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    Limits just work off of temp. If that's the right code, something is over temp or a bad limit switch. Is the blower fan running? If only running for 20 secs i would not think any limit would get that hot that quick. Sounds like a service tech visit is in order.
    UA Local 32 retired as of Jan 2020

  4. #4
    Join Date
    Jan 2020
    Posts
    2
    Post Likes
    Thread Starter
    The blower fan does run but I agree, I just called a tech. Appreciate it.

  5. #5
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    4,434
    Post Likes
    Post the results.
    UA Local 32 retired as of Jan 2020

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