Your heat pump's outdoor unit has detected a problem with a temperature sensor that monitors the cooling fluid, preventing the system from heating your home efficiently.

Outdoor Unit, Compressor Refrigerant Return Thermistor (Th) Error

What causes this fault?

This fault occurs when the control system receives an illogical or missing temperature reading from the sensor monitoring the liquid returning to the compressor. It is usually caused by the sensor itself failing internally or a break in the electrical wiring connecting the sensor to the main control board. Without this data, the unit shuts down to prevent potential damage to the refrigeration cycle.