Controls · COMPONENT REFERENCE

Heat-pump defrost control troubleshooting

Coordinates defrost logic and the documented reversing-valve and fan outputs on applicable heat pumps.

Failure causes

Choose a cause for symptoms, checks that separate it from similar faults, repair direction and verification.

Failed output or control board →The board does not deliver a required output despite valid power, inputs and operating conditions.Sensor, harness or input fault →An inaccurate or missing input prevents the board from recognizing the proper operating state.

References and applicability

Original HVACSim explanations with manufacturer and instrument-maker references for further reading. These resources support the subject; their model-specific examples are not specifications for every system.

Resideo: RTH6360 thermostat installation and setupExamples of heat-pump O/B and staging setup. Menu numbers vary by thermostat.
Copeland: CoreSense diagnostics for scroll air-conditioning compressors (AE8-1379)Model-specific diagnostic examples; flash codes are not universal.

Editorial review: 2026-09-29. Verify the current manual for the installed model.