Refrigerant Pressure Sensor / Switch: Description and Operation
A/C PRESSURE TRANSDUCERThe A/C pressure transducer is a switch that is installed on a fitting located on the refrigerant liquid line between the receiver/drier and the expansion valve in the right rear corner of the engine compartment. An internally threaded hex fitting on the transducer connects it to the externally threaded Schrader-type fitting on the liquid line. A rubber O-ring seals the connection between the transducer and the liquid line fitting. Three terminals within a molded plastic connector receptacle on the top of the transducer connect it to the vehicle electrical system through a wire lead and connector of the headlamp and dash wire harness.
The A/C pressure transducer cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
The A/C pressure transducer monitors the pressures in the high side of the refrigerant system through its connection to a fitting on the liquid line. The transducer will change its internal resistance in response to the pressures it monitors. The power-train control module (PCM) provides a five volt reference signal and a sensor ground to the transducer, then monitors the output voltage of the transducer on a sensor return circuit to determine refrigerant pressure. The PCM is programmed to respond to this and other sensor inputs by controlling the operation of the A/C compressor clutch and the radiator cooling fan to help optimize air conditioning system performance and to protect the system components from damage. The A/C pressure transducer input to the PCM will also prevent the A/C compressor clutch from engaging when ambient temperatures are below about 4.5° C (40° F) due to the pressure/temperature relationship of the refrigerant. The Schrader-type valve in the liquid line fitting permits the A/C pressure transducer to be removed or installed without disturbing the refrigerant in the system. The A/C pressure transducer is diagnosed using a DRBIII(R) scan tool. Refer to Body Diagnostic Procedures.