A/C Compressor

A/C Compressor

The A/C (air conditioning) compressor circulates the refrigerant around the system by compressing low pressure, low temperature vapor from the evaporator and discharging the resultant high pressure, high temperature vapor to the condenser. The A/C (air conditioning) compressor installed on 3.0L Diesel models is different to the one installed on 4.2L and 4.4L models.

4.2L and 4.4L A/C Compressor







On 4.2L and 4.4L models, the A/C (air conditioning) compressor is a variable displacement unit attached to a mounting bracket on the front left side of the engine. The secondary accessory drive belt, driven by the engine crankshaft, drives the A/C (air conditioning) compressor via a pulley and an electromagnetic clutch. Operation of the clutch is controlled by a power feed from the ATC (automatic temperature control) module.

The A/C (air conditioning) compressor is a 7 cylinder swashplate unit with a minimum displacement of 5.5 cu.cm/rev (0.34 cu.in/rev) and maximum displacement of 163 cu.cm/rev (9.95 cu.in/rev). A control valve in the A/C (air conditioning) compressor automatically adjusts the displacement (i.e. flow of refrigerant), between the minimum and maximum values, to match the thermal load of the evaporator. By matching the refrigerant flow to the thermal load of the evaporator, the variable A/C (air conditioning) compressor maintains a relatively constant evaporator temperature of approximately 3 to 4 degrees C (37 to 39 degrees F).

To protect the refrigerant system from unacceptably high pressure, a pressure relief valve is installed in the outlet side of the A/C (air conditioning) compressor. The pressure relief valve is set to open at 3.5 to 4.1 MPa (508 to 595 lbf/sq.in) and vents excess pressure into the engine compartment. The pressure relief valve closes again when the pressure decreases to 3.01 MPa (437 lbf/sq.in).

The clutch of the A/C (air conditioning) compressor incorporates a thermal cut-off fuse, which disconnects the power feed from the ATC (automatic temperature control) module if the temperature increases to 182 ± 5 degrees C (360 ± 9 degrees F).