Compressor HVAC: Description and Operation

The HD6/HT6 Automotive Conditioning Compressor and Clutch Assembly is a lightweight, six cylinder axial design. The HD6/HT6 has three double ended pistons. The HD6IHT6 weighs 5.8 kg (12.7 lbs).

Although the HD6IHT6 compressor is the same for all vehicle applications, differences in the following features exist:
- Installations
- Mounting brackets
- Pulleys
- Torque cushions
- Switches

None of the above differences affects the overhaul procedures.

The following two clutch driver designs exist for the HD6/HT6 compressors:
- A clutch driver without a torque cushion (1)
- A clutch driver with a torque cushion (2)

Service compressors are supplied with one of the following components:
- The control switches assembled in the rear head
- A plug located where a control switch is required

Perform the following steps if the service compressor requires control switches:
1. Remove the plug from the appropriate rear head switch cavity of the replaced compressor.
2. Replace the compressor and assemble the compressor as directed in this manual.

Prevent dirt or foreign material from getting on or into the compressor components and system when servicing the compressor. Clean tools and a clean work area are important for proper service. Clean the compressor connections and the outside of the compressor before any on-vehicle repairs or before removing the compressor. Ensure that the components remain clean at all times. Clean any parts that need to be reassembled with one of the following cleaning agents:
- Trichloroethane
- Naphtha
- Stoddard solvent
- Kerosene or equivalent

Dry the components with dry air. Use a non-lint producing type of cloth if using a cloth is necessary. The following operations are based on bench overhaul with the compressor removed from the vehicle unless noted. The operations are prepared in order of the accessibility of the components. Perform the following steps when removing a compressor from the vehicle for service:
1. Drain the amount of PAG lubricant remaining in the compressor.
2. Measure the amount of PAG lubricant drained.
3. Record the measurement.
4. Discard the drained PAG lubricant.
5. Add an equal amount of new PAG lubricant to the compressor.

The service compressor is shipped with 240 ml (8 oz) of PAG lubricant. Drain and retain the PAG lubricant for use as replacement lubricant when service procedures require addition of new lubricant to the compressor. Replace the lubricant only with GM approved PAG oil P/N 12345923.

Most minor repair procedures do not require you to discharge the system. Major repair procedures require you to discharge the system of refrigerant.