What happens
The motor cannot operate because its required supply or PSC capacitor circuit is incomplete.
Typical symptoms
Fan does not start even though its isolated winding checks appear plausible.
Checks that distinguish this cause
Trace the supply and motor leads, and test the correctly isolated capacitor if the motor uses one. Do not attempt a hand-assisted start.
What can look similar
Correct voltage without a correct command may be normal on an electronically controlled motor.
Repair direction
Repair the verified lead, connection or capacitor fault using approved specifications.
Verify the repair
Verify normal automatic start, stop and outdoor airflow.
Equipment-specific limits
Identify PSC, ECM or other motor technology and rotation requirements. Keep clear of automatic starts and moving blades.
Practice this diagnosis
This cause is a reference topic; it does not yet have a dedicated simulated call. Browse the practice board.
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.
- Copeland: CoreSense diagnostics for scroll air-conditioning compressors (AE8-1379)Model-specific diagnostic examples; flash codes are not universal.
- Fluke: How to measure capacitancePower isolation, discharge and capacitance measurement.
Editorial review: 2026-09-29. Verify the current manual for the installed model.