Electrical · COMPONENT REFERENCE

Control wiring and splices troubleshooting

Carries power and calls between thermostat, indoor controls and outdoor equipment. Terminal function comes from the diagram, not wire color.

Failure causes

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

Open R or C conductor →A disconnected or broken supply or return interrupts a complete control-power circuit.Open Y, G, O/B or Y2 conductor →The commanded signal cannot reach the load or controller because its conductor is interrupted.Shorted or pinched cable →Two unintended conductors touch, or a conductor touches a grounded cabinet through damaged insulation.High-resistance splice or terminal →A loose or corroded connection restricts current without being completely open.

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.

Fluke: HVAC and industrial electrical testing applicationsElectrical measurement principles, including control-circuit voltage references.
Resideo: RTH6360 thermostat installation and setupExamples of heat-pump O/B and staging setup. Menu numbers vary by thermostat.

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