Front A/C Pressure Transducer - 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 Engine Control Module (ECM). The ECM is programmed to respond to this and other sensor inputs by controlling the operation of the swash plate 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 ECM adjusts the swash plate to nearly a zero degree angle (low compressor displacement) when high side pressure rises above 3130 kPa (454 psi) and re-adjusts the swash plate to a greater angle (higher compressor displacement) when high side pressure drops below 1999 kPa (290 psi). The ECM also reduces the swash plate angle if the high side pressure drops below 200 kPa (29 psi) and will increase the swash plate 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 ECM will actuate the radiator cooling fan.

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

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

ELECTRIC A/C CONDENSER COOLING FAN SWITCH POINT