Compressor Clutch: Description and Operation

A/c Compressor Clutch:

The A/C compressor clutch assembly consists of a stationary electromagnetic field coil, a hub bearing and pulley assembly, and a clutch plate. The field coil and the hub bearing and pulley assembly are each retained on the nose of the compressor front housing with snap rings. The clutch plate is splined to the compressor shaft and secured with a bolt.

The compressor clutch plate and pulley and the clutch field coil are available for service replacement.

The compressor clutch components provide the means to engage and disengage the compressor from the engine serpentine accessory drive belt. When the clutch coil is energized, it magnetically draws the clutch into contact with the pulley and drives the compressor shaft. When the coil is not energized, the pulley freewheels on the clutch hub bearing, which is part of the pulley.

The compressor clutch engagement is controlled by several components:
- A/C switch on the A/C-heater control panel
- Evaporator temperature sensor
- A/C pressure transducer
- Air temperature sensor
- CAN bus messages

The compressor clutch is de-energized under any of the following conditions:
- Blocked compressor (thermal fuse in the pulley)
- Low pressure in the system
- Low evaporator temperature
- Hard acceleration (WOT)
- High coolant temperatures