Fault Phenomenon: Putzmeister M56 AC functions normally when cold. In high-temperature environments (operating temperature), the AC compressor seizes, the belt burns, and eventually the engine overheats.

Troubleshooting Process:
– Checked refrigerant pressure: pressure normal.
– Checked compressor clutch: coil normal.
– Checked belt tension: tension normal.
– Measured compressor rotational resistance at operating temperature: found infinite resistance.

Root Cause: The internal bearings of the AC compressor lack lubrication and seize due to heat.

Required Parts: AC compressor assembly and belt.