Compressor HVAC: Description and Operation

A/C COMPRESSOR AND CLUTCH ASSEMBLY

NOTE: Internal FS18/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 clutch field coil are serviceable.

The FS18/FS20 A/C compressor has the following characteristics:
- A non-serviceable shaft seal
- A pressure relief valve is installed in the rear of the compressor to protect the refrigerant system against excessively high refrigerant pressures
- The A/C compressor uses PAG oil or equivalent. This oil contains special additives required for the A/C compressor
- The A/C compressor 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







When battery voltage is applied to the A/C clutch field coil, the clutch disc and hub assembly is drawn toward the A/C compressor pulley. The magnetic force locks the clutch disc and hub assembly and the A/C compressor pulley together as one unit, causing the compressor shaft to rotate. When battery voltage is removed from the A/C clutch field coil, an annular ring in the clutch disc and hub assembly moves the clutch disc away from the A/C compressor pulley.