What happens
A broken conductor or disconnected connector prevents power from reaching the motor.
Typical symptoms
Good upstream voltage and plausible motor tests, yet one or more loads remain silent.
Checks that distinguish this cause
Trace the diagram from control output to the motor terminals. With safe isolation, inspect connectors and test the separated lead end to end.
What can look similar
An open motor winding appears similar until the harness and winding are tested separately.
Repair direction
Repair approved wiring and connectors, protecting them from abrasion, heat and strain.
Verify the repair
Verify voltage at the destination and normal operation of every affected load.
Equipment-specific limits
Protective earth is not a substitute for neutral. An open neutral must not be repaired by adding a neutral-to-chassis bond at equipment.
Practice this diagnosis
These simulated calls exercise this component or repair family. The article describes a broader diagnostic process; a call may represent a different cause within that family.
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.
- Copeland: Compressor terminal venting safetyStop conditions and hazards around compressor electrical terminals.
Editorial review: 2026-09-29. Verify the current manual for the installed model.