Display shows F5, and the unit may not defrost properly (heat pump models) or may shut down.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Failed outdoor defrost thermistor, sensor not properly attached to the coil, damaged wiring, defective defrost control on the outdoor PCB.

Safety: Turn off power to the heat pump at the disconnect.

Steps:

Locate defrost sensor: Typically clipped to the outdoor coil tubing on Comfortmaker heat pumps.
Check attachment and position: Ensure firm contact with the coil and that it is not hanging loose.
Inspect wiring and connector: Repair any damaged wires and reseat the connector on the PCB.
Test resistance: Compare sensor resistance to the thermistor chart. Replace if out of range.

Note: If the sensor is good but F5 persists, the defrost control function on the outdoor board may be faulty.

Hard 4/5

Defrost Temperature Sensor

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