What happens
Restricted cooling or an impaired thermal interface raises power-device temperature during operation.
Typical symptoms
Drive trips after running or fails mainly during warm weather despite acceptable input supply.
Checks that distinguish this cause
Check the model-required air path, fan behavior and heat-sink condition with power safely isolated. Compare recorded thermal behavior with the service procedure; inspect mounting and thermal materials only where service is permitted.
What can look similar
High compressor load or an inaccurate temperature input can produce a similar thermal protection event.
Repair direction
Restore the approved cooling arrangement or replace damaged approved parts; use the specified thermal materials and mounting method.
Verify the repair
Verify sustained operation under the previously failing ambient and demand conditions.
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.