Notice: The refrigeration system on these models uses R-134a which is not compatible with refrigerant R-12. Before servicing the system always make sure the proper servicing equipment is used or the system could become severely damaged. Always refer to the service text and manufacturer's instructions included with service equipment before proceeding.
Two different air conditioning systems are available depending upon the engine application:
- The Variable Displacement Orifice Tube (VDOT) refrigerant system is used on vehicles that are equipped with 2.2L engines. These systems use the constant run Harrison V7 compressor.
- The Cycling Clutch Orifice Tube (CCOT) refrigerant system is used on vehicles that are equipped with 4.3L engines. These systems use the fixed displacement Harrison HT6 compressor.
A/C Refrigerant Pressure Sensor (2.2L)
The A/C refrigerant pressure sensor is a pressure transducer, which is located between the compressor and condenser, provides low and high pressure protection for the A/C system. The sensor provides a signal to the PCM. The signal is directly related to the refrigerant pressure in the A/C lines. When the pressure is high then the sensor provides a high voltage to the PCM. Similarly, Low pressure produces a low signal voltage. The PCM is calibrated to shut the A/C compressor OFF if the refrigerant pressure is too low or too high.
High Pressure Cutout Switch (4.3L)
The high pressure cutout switch is a normally closed switch, which is located at the rear of the compressor, provides high pressure protection for the A/C system. The switch opens when the refrigerant pressure exceeds a preset value. The switch closes once the refrigerant pressure decreases to a "normal" level. The switch is connected in series with the A/C request circuit. Whenever the switch opens, the A/C request state changes from ON to OFF. The VCM turns the A/C compressor OFF once the A/C request is in the OFF state.
Low Pressure Cycling Switch (4.3L)
The low pressure cycling switch is a normally closed switch, which is located between the evaporator and accumulator, provides low pressure protection for the A/C system. The switch opens when the refrigerant pressure drops below a preset value. The switch closes once the refrigerant pressure increases to a "normal" level. An open switch provides the VCM with a signal that the VCM uses to turn OFF the A/C compressor.
