What happens
The output stage reports an abnormal condition or cannot drive the compressor. A protection report can arise from the motor or operating conditions as well as the module.
Typical symptoms
Compressor attempts to start, then stops with an inverter or current fault.
Checks that distinguish this cause
Preserve fault history and check supply, motor connections, cooling and the compressor using the exact drive procedure. Follow the documented separation of compressor and module tests; ordinary AC voltage readings on PWM output are not a universal pass/fail test.
What can look similar
A grounded compressor, locked mechanism or poor power connection can trigger output protection on an intact drive.
Repair direction
Correct the established supporting fault or replace a confirmed failed approved drive, including required setup.
Verify the repair
Verify the compressor across the permitted speed range and confirm protection does not recur.
Equipment-specific limits
Inverter electronics can retain dangerous DC voltage after supply isolation. Isolate all inputs, follow the specified discharge wait and prove the designated circuit safe with the OEM method. Never short a DC bus to discharge it, unplug powered motor connectors or insulation-test through connected electronics.
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.
- Haier: Arctic Next Gen service manualAW/1U EH2VHD model examples of inverter, motor, sensor and circuit diagnostics; obtain the installed model manual.
- Daikin: 17 Series service manualModel-specific sensor and control examples; terminal values and code definitions vary.
Editorial review: 2026-09-29. Verify the current manual for the installed model.