What happens
Mechanical damage can prevent rotation or reduce pressure lift even when electrical paths are intact.
Typical symptoms
Repeated failed starts or a running compressor with inadequate refrigeration performance.
Checks that distinguish this cause
Rule out supply, capacitor, staging, reversing-valve bypass and load conditions first. Compare current and pressures with the compressor manufacturer's diagnostic method, not a generic pressure target.
What can look similar
Low charge and valve bypass can imitate weak pumping. Reverse rotation is a distinct possibility only on applicable three-phase models.
Repair direction
Repair the proven supporting fault or replace a confirmed mechanically failed compressor using the approved procedure.
Verify the repair
Verify the expected capacity, pressure behavior and current at known operating conditions.
Equipment-specific limits
Single-phase C/R/S checks do not apply to every inverter or three-phase compressor. Use model data, isolate electronics as directed and never run or perform insulation tests under vacuum.
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.
- Copeland: Refrigeration basics: troubleshooting fundamentalsCompressor and refrigerant troubleshooting concepts, not a charging specification.
- Copeland: Compressor terminal venting safetyStop conditions and hazards around compressor electrical terminals.
- Fluke: Insulation resistance and electrical testing for HVAC compressor motorsInsulation-testing precautions, including avoiding tests under vacuum; use compressor-specific instructions.
Editorial review: 2026-09-29. Verify the current manual for the installed model.