What happens
A resistive terminal drops voltage and heats when motor current flows.
Typical symptoms
Intermittent start, weak hum or abnormal heating; unloaded measurements may look healthy.
Checks that distinguish this cause
A qualified technician localizes the drop during the failure. Isolate before inspecting or tightening; use specified torque and replace damaged terminals.
What can look similar
A motor fault may raise current and heat an otherwise marginal connection. Both may need correction.
Repair direction
Renew the damaged connection with approved parts and address environmental damage.
Verify the repair
Verify operating voltage and connection condition under sustained 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
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.
- 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.