Controls · COMPONENT REFERENCE

Thermostat troubleshooting

Requests heating, cooling, fan operation and, on compatible systems, reversing-valve and stage commands.

Failure causes

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

Missing thermostat power →An open R or C path, missing transformer supply or depleted batteries prevents normal operation.Missing or stuck output →A thermostat output fails to issue or release the commanded signal.Wrong heat-pump or staging setup →The thermostat is configured for a different equipment type, changeover logic or number of stages.

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.
Fluke: HVAC and industrial electrical testing applicationsElectrical measurement principles, including control-circuit voltage references.

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