Compressor HVAC: Description and Operation

A/C COMPRESSOR AND CLUTCH ASSEMBLY

NOTE:
- Internal A/C compressor components are not serviced separately. The SC115 A/C compressor is serviced only as an assembly. The clutch disc and hub, the clutch pulley and bearing, and the clutch field coil are serviceable.
- Installation of a new suction accumulator is not required when repairing the air conditioning system except when there is physical evidence of system contamination from a failed A/C compressor or damage to the suction accumulator.

The SC115 A/C compressor has the following characteristics:
- Tangential mount design: 3 lugs.
- The single manifold block of the compressor manifold and tube assembly fits to the suction and discharge ports. Two O-ring seals are used for sealing.
- An eccentric bushing is driven by the shaft of the A/C compressor.
- An orbiting scroll driven by the eccentric bushing compresses the refrigerant gas against the walls of the fixed scroll.
- Single reed-type discharge valve mounted on the back of the fixed scroll. There are no suction valves.
- Non-serviceable shaft seal fully supported on both sides by bearings.
- 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 - 6.0L Diesel:

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.

A/C Pressure Relief Valve
An A/C pressure relief valve is incorporated to:
- relieve unusually high refrigerant system discharge pressure buildups. For specifications regarding operating pressure(s), refer to Heating and Air Conditioning.
- prevent damage to the A/C compressor and other system components.
- avoid total refrigerant loss by closing after the excessive pressure has been relieved.