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    barker7's Avatar
    barker7 Posts: 1, Reputation: 1
    New Member

    Jul 3, 2006, 07:47 AM
    Heat pump AHU fan runs continuously
    I have a 12 year old Trane Xe1000 heat pump. Recently I noticed that the fan keeps running continuously even when the outside unit turns off. It's as if the tstat fan switch is set to On (it's not) instead of Auto. I tried a few things:

    1) In the tstat (weathertron) I disconnected the fan control wire (green). Fan kept running.

    2) I killed the power via the breaker. System shut down (including the fan). After re-powering the system, the fan DID properly cut off after the cooling cycle. But a day later, the problem is back

    I opened the AHU access panel and according to the wiring diagram there is a fan delay relay (FDR). That could be sticking. I've also seen some other posts around the internet talking about the FDR on a Trane. What's the best way to check this relay (I'm experienced (and cautious) around electricity).
    Wha other components could fail?


    Arby22's Avatar
    Arby22 Posts: 2, Reputation: 1
    New Member

    Jun 24, 2009, 07:53 PM

    I had the same problem. The relay to the fan turn off the immediately turn back on. Just in the cooling, heating was fine. I had an old mechanical mercury switch Honeywell therostat. Changed t-stat to a new Honeywell, works fine. Be sure to label you wires before unwiring old t-stat.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert

    Jun 25, 2009, 03:15 AM
    I would check the A/C fan relay in the inside unit first. If you disconnect the fan wire in the thermostat and the fan still runs it is a good possibility the relay is stuck/defective.

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