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  1. #1
    Join Date
    May 2007
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    Trane 4 Ton Heat Pump RTU

    Trane 5 Ton RTU^^^^^

    Trane convertable Rooftop package, single cool, 2 heat(1 mechanical, 1 electric) 4WCC3060 5 Ton Unit with Demand Defrost Control(Coil Sensor + Outdoor Temp Sensor)

    Found unit running in heat, condensor coil iced over completely, solid block of ice. Unit not going into defrost automatically. Its one of those trane boards with the frc defrost/ test common/ + test pins. When i short frc defrost and test common, the unit goes into defrost no problems.

    I ohmed out my sensors and both were reading below required defrost conditions! replaced board, same problem! going back monday, left electric heat on and letting coil defrost to confirm location of sensors.

    any suggestions?

  2. #2
    Join Date
    Dec 2004
    Columbia South Carolina
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    Check sensors

    you need to ohm out your sensors. The troubleshooting chart in the unit tells you what the resistance should be depending on what the current temperature the sensor is sensing. Take the temp readings as close as possible to the sensor, mesaure the resistance on your meter on the 200K setting and compair. if the readings are way off, replace the sensors.

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