Compressor HVAC: Description and Operation

Air Conditioning

A/C Compressor and Clutch Assembly

NOTE: Internal FS18 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 clutch field coil are serviceable.

NOTE: Installation of a new suction accumulator is not required when repairing the A/C system except when there is physical evidence of system contamination from a failed A/C compressor or damage to the suction accumulator.

The FS18 A/C compressor:

- uses a non-serviceable shaft seal.
- has a pressure relief valve installed in the rear of the compressor to protect the refrigerant system against excessively high refrigerant pressures.
- uses PAG oil or equivalent. This oil contains special additives required for the A/C compressor.
- PAG oil may have some slightly dark-colored streaks while maintaining normal oil viscosity. This is normal for this A/C compressor because of break-in wear that can discolor the oil.

Use standard oil matching procedures when installing new compressors.

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 plate and hub assembly is drawn toward the A/C clutch pulley.
- The magnetic force locks the clutch plate 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 plate and hub assembly move the clutch plate away from the A/C clutch pulley.