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  1. #1

    Heater fan cycles on long and longer then stays on when thermostat calls for heat....

    and also cycles a couple times when it is shutting down. I've read about the fan limit switch but I don't see one in my unit. It draws air from the top of a townhouse so it isn't drawing in cold air if that helps. The pilot lights fine, ignites 2 large flames fine, and then fan kicks on fine, but fan cycles off then on, then off, then on a few times until it stays on.

    I can see 2 solenoid switches. One switches on and off versus just turning on. I have no idea, but I wonder if there is a temperature sensor that isn't getting warm enough so when the fan kicks on it thinks it's still too cold and shuts the fan off? Thanks in advance.

    edit: I forgot to mention it does have a delay switch on the same circuit board as the solenoid switches so I adjusted that but nothing changed.
    Last edited by Jeffrimerman; 12-22-2012 at 03:04 PM. Reason: add info

  2. #2
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    6,356
    Does the pilot stay lit all the time or lights each time there is a call for heat? Model and serial would help. If it has a fan limit what you described happens when the return air its pulling in is cold and cools the fan limit down as the heat exchanger is warming or if there is an airflow restriction or blocked chimney it will overheat the fan limit and cause the fan to run more than it should trying to keep the hx cool

  3. #3
    The pilot lights each time there is a call for heat. It stays on for a while before kicking on the flames. I checked, but none of the stickers mention model number. Hopefully you can see this pic and get an idea. I don't think it has a fan limit switch, but maybe you can see from this pic. There is a clear tube that seems to carry air to a circular looking thing in the middle of the pic. When this is disconnected the system shuts down before the fan even comes on.
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  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,897
    Given the age, I'd have a pro check it out. While he's at it, need to get the flex connector from entering the cabinet, that's dangerous.

  5. #5
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    6,356
    Might be time for a new furnace, Its likely the heat exchanger has failed. Have a pro come check it out.

  6. #6
    Yes, that's probably what I'll do. It's the original one, and the AC doesn't work so well either so 2 birds, 1 stone should take care of both. Thank you

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