What happens
A supply, connection or internal power-conversion fault prevents the drive from establishing its required operating supply.
Typical symptoms
Outdoor electronics do not start, restart under demand or report a power-related fault.
Checks that distinguish this cause
Qualified personnel trace the model diagram from supply to the designated power-conversion checkpoints. Compare no-demand and demand behavior using the specified test method, separating an upstream interruption from an internal conversion failure.
What can look similar
A control inhibit can leave the compressor stopped with a healthy power stage; a blank indoor display may instead be an indoor power fault.
Repair direction
Restore the verified supply or connection defect, or replace the approved failed module after checking its loads.
Verify the repair
Confirm stable supply and the documented drive startup with no repeat fault.
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.