Compressor HVAC: Description and Operation

The HD6/HT6 Automotive Conditioning Compressor and Clutch Assembly is a light weight, six cylinder axial design consisting of three double ended pistons and weighs 5.8 kg (12.7 lb..)

Although this compressor is the same for all vehicle applications, there are differences in installations, mounting brackets, pulleys, torque cushions and switches, none of which will affect the following overhaul procedures.




This compressor has a clutch driver design without torque cushion (1).

Service compressors are supplied with either the control switches assembled in the rear head or a plug may be found where a control switch is required. If the service compressor requires control switches, the plug may be removed from the appropriate rear head switch cavity of the replaced compressor and assembled.




When servicing the compressor, keep dirt or foreign material from getting on or into the compressor parts and system. Clean tools and a clean work area are important for proper service. The compressor connections and the outside of the compressor should be cleaned before any "on vehicle" repairs, or before removal of the compressor. The parts must be kept clean at all times and any parts to be reassembled should be cleaned with solvent, and dried with dry air. When necessary to use a cloth on any part, it should be of a non-lint producing type.

The operations described below are based on bench overhaul with the compressor removed from the vehicle, except as noted. They have been prepared in order of accessibility of the components. When a compressor is removed from the vehicle for servicing, the amount of PAG lubricant remaining in the compressor should be drained, measured and recorded. This PAG lubricant should then be discarded and an equal amount of new PAG lubricant added to the compressor.

The service compressor is shipped without PAG oil. When service procedures require, use only Isuzu approved PAG oil.

Metric Thread Size Information
Compressor to mounting bracket bolts (Front)
M10 x 1.5 - 6 H

Compressor to mounting bracket bolts (Rear)
M8 x 1.25 - 6 H

Suction-discharge port screw
M10 x 1.5 - 6 H

Compressor shaft
M9 x 1.25 - 6 H

Internal hub-clutch drive assembly
M22 x 1.5 - 6 H