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  1. #1

    Intermittent Problem - Blower Will Not Turn Off

    I'm hoping someone here can help solve a problem that has mystified everyone else.

    I have a Coleman Heat Pump (HC8B036F1) and modulating furnace (FC9C080C16DH11). It generally runs fine without any issues except for one intermittent problem.

    Every few days, following a heating or cooling cycle, the blower will go to around 70% and stay there indefinitely. It continues to run even though the thermostat is no longer calling for heating or cooling.

    I know the thermostat is not calling for the fan as I can turn it to the OFF position, and the blower keeps going. I've even pulled the thermostat face off the wall, which would prevent any signal from being sent, and the blower still runs. The only thing I can do to stop the fan is to manually set the thermostat up or down (until the "Heat On" or "Cool On" appears on the thermostat) and then cancel the temporary setting so that the "Heat On" or "Cool On" disappears. When I do this, the thermostat clicks on and off, and then the blower turns off after a few seconds.

    When this intermittent problem occurs, if I do nothing, the blower will continue to run until the next heating/cooling cycle, at which time the blower will stop as it normally would after the thermostat clicks off. The only other way to stop the blower when it gets stuck like this is to cycle AC power to the furnace.

    When this problem occurs, it is always after the heat pump outdoor unit has turned off and the furnace is not producing any heat. The settings on the furnace board are:

    RECIRC = C
    DELAY = A
    COOL = A
    ADJUST = A
    AIR = NOM

    There are no stored error messages.

    I have had this intermittent problem since the day the furnace and heat pump were installed. I reported the problem to the dealer who later came and replaced the motherboard under warranty, but to no avail.

    Not sure where to go from here. Any ideas or suggestions would be appreciated.

  2. #2
    Join Date
    Oct 2012
    Location
    kansas
    Posts
    9
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

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    Last edited by beenthere; 10-18-2012 at 06:04 AM. Reason: Non Pro * Member

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,760
    gearhead3, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Your post has been deleted.
    Further infractions may result in loss of posting privileges.
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  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,760
    The system switch on your thermostat has no control over the fan, so just because its in the off setting, doesn't mean the thermostat isn't calling for the fan to run. If your thermostat is programmable. Make sure non of the programmed events have the fan set to on.
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  5. #5
    Quote Originally Posted by beenthere View Post
    The system switch on your thermostat has no control over the fan, so just because its in the off setting, doesn't mean the thermostat isn't calling for the fan to run. If your thermostat is programmable. Make sure non of the programmed events have the fan set to on.
    Thanks for the reply. When this intermittent problem occurs, I can physically remove the thermostat from the wall and the blower continues to run. This occurs randomly, with no apparent pattern. Sometimes it will go for more than 7 days without a problem so I know it's not tied to a programmed event.

    Are there any circumstances in which the blower will continue to run on its own, apart from the thermostat commanding the fan on?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,760
    High limit trip.
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