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What actions are recommended if my Ruud Ultra Plug-in Heat Pump with HydroBoost (120V Shared Circuit) shows Alarm Code A102?

CAUTION: For your safety, DO NOT attempt repair of electrical wiring, controls, heating elements, or other safety devices. Refer repairs to qualified service personnel.

Possible Cause: Heating source defaults to elements due to heat pump temperature sensor malfunction. What To Do:

  1. Carefully inspect the connections of the wiring and sensors.
  2. If you have access to a multimeter, determine the Ohm reading on the thermistors. Always refer to the Ohm chart to correlate the readings with the prevailing ambient temperature.
  3. Using the device’s interface, navigate to Service –> Sensors. Should the sensor display a -40°F reading, it indicates the circuit is open. Conversely, a +250°F reading means the circuit has shorted. To validate this, power down the unit, disconnect the thermistor from its board, and recheck the Ohm reading.

This answer is applicable for the following model: Ruud Ultra Plug-in Heat Pump with HydroBoost (120V Shared Circuit).

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