Operation

OPERATION

The front A/C pressure transducer monitors the pressures in the high side of the front refrigerant system through its connection to the A/C liquid line, by use of a port on the refrigerant line tapping block located on the left end of the front A/C condenser. The front A/C pressure transducer will change its internal resistance in response to the pressures it monitors.

The A/C-heater control provides a five volt reference signal to the A/C pressure transducer, then monitors the output voltage of the front A/C pressure transducer on a sensor return circuit to determine front refrigerant system pressure. The control broadcasts a refrigerant pressure message to the powertrain control module (PCM) or the engine control module (ECM) (depending on engine application). The PCM/ECM is programmed to respond to this and other sensor inputs by controlling the operation of the swashplate within the front A/C compressor and the radiator cooling fan to help optimize front A/C system performance and to protect the system components from damage. The PCM/ECM adjusts the swashplate to nearly a zero degree angle (low compressor displacement) when high side pressure rises above 3130 kPa (454 psi) and re-adjusts the swashplate to a greater angle (higher compressor displacement) when high side pressure drops below 1999 kPa (290 psi). The PCM/ECM also reduces the swashplate angle if the high side pressure drops below 200 kPa (29 psi) and will increase the swashplate angle when the high side pressure rises above 234 - 262 kPa (34 - 38 psi). When the front refrigerant system pressure rises above 1655 kPa (240 psi), the PCM/ECM will actuate the radiator cooling fan.

The front A/C pressure transducer is diagnosed using a scan tool.

The front A/C pressure transducer cannot be adjusted or repaired and must be replaced if inoperative or damaged.