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  1. #1
    Join Date
    Feb 2004
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    Trane Mod# TWY048B100A heat pump with Var. Speed cond fan... System is colling well, its 90+ outside but the fan is ramping up to full speed then shuts down only to ramp up again. It repeats the cycle ever few seconds. I went over the wiring diagram. In the cond fan control circuit it shows an outdoor fan stat, a fan control board, the defrost control board and the motor, but doesnt explain a sequence of events, or what is actually happening inside the boards. I jumped the fan stat and replaced the fan control board with a new one... No Change... I dont want to order a replacement motor unless Im sure. Also after I left I realized that I although I had jumped the fan stat I didnt pull a wire off it and open the switch to see if this changed anything. Does anyone know how its suppose to work so I can properly troubleshoot.

  2. #2
    Join Date
    Jun 2003
    Post Likes
    It sounds identical to the new Carriers I had installed. The condenser fan operates off of a fan control which senses the condensing pressure, and ajusts the fan speed(up or down) to try to maintain 225lbs of head pressure. This allows the system to run in low ambient temps, and more efficiently in all temps. Look at your gauges while it's doing this....might be nothing wrong, just scary.

    Someone will correct me if Trane isn't doing the same thing.

    If everything was always done "by the book"....the book would never change.

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