Compressor HVAC: Description and Operation

A/C Compressor and Clutch Assembly

NOTE: Internal FS20 A/C compressor components are not serviced separately. The A/C compressor is serviced only as an assembly. The clutch disc and hub, A/C compressor pulley and bearing and the clutch field coil are serviceable.

The FS20 A/C compressor uses the following:

- A non-serviceable shaft seal
- A pressure relief valve installed in the rear of the compressor to protect the refrigerant system against excessively high refrigerant pressures as a redundant backup to the A/C pressure transducer
- PAG oil or equivalent. This oil contains special additives required for the A/C compressor

Use the refrigerant oil adding procedure specified for this vehicle when installing a new A/C compressor.

A/C Compressor Clutch Assembly









The magnetic A/C clutch has the following characteristics:

- The A/C clutch drives the compressor shaft
- When battery positive voltage (B+) is applied to the A/C clutch field coil, the clutch disc and hub assembly is drawn toward the A/C clutch pulley
- The magnetic force locks the clutch disc and hub assembly and the A/C clutch pulley together as one unit, causing the compressor shaft to rotate
- When B+ is removed from the A/C clutch field coil, springs in the clutch disc and hub assembly move the clutch disc away from the A/C clutch pulley