Fault Phenomenon: SANY SW956 wheel loader after turning on the AC, the compressor runs continuously without cycling off, causing the evaporator to freeze and no airflow.

Troubleshooting Process:
– Checked thermostat: evaporator temperature sensor failed.
– Checked clutch: clutch coil constantly energized or mechanically seized.
– Checked relay: AC relay contacts welded.
– Checked refrigerant: refrigerant pressure switch faulty.

Root Cause: The AC compressor electromagnetic clutch supply relay contacts welded due to high temperature, preventing the clutch from de-energizing and disengaging.

Required Parts: Replace AC compressor relay.