Refrigerant Pressure Sensor / Switch: Description and Operation

A/C Pressure Transducer:

The A/C pressure transducer is a switch that is installed on a fitting located on the A/C discharge line. An internally threaded fitting on the transducer connects it to the externally threaded Schrader-type fitting on the A/C discharge line. A rubber O-ring seals the connection between the transducer and the discharge line fitting. The A/C pressure transducer is connected to the vehicle electrical system by a molded plastic connector with three terminals.

The A/C pressure transducer monitors the pressures in the high side of the refrigerant system through its connection to a fitting on the A/C discharge line. The A/C pressure transducer will change its internal resistance in response to the pressures it monitors. A Schrader-type valve in the discharge line fitting permits the A/C pressure transducer to be removed or installed without disturbing the refrigerant in the A/C system.

The powertrain control module (PCM) provides a five volt reference signal and a sensor ground to the A/C pressure transducer, then monitors the output voltage of the A/C pressure 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 A/C system performance and to protect the system components from damage. The PCM will disengage the A/C compressor clutch when high side pressure rises above 2971 kPa (431 psi) or falls below 206 kPa (30 psi). The A/C pressure transducer input will also disengage the A/C compressor clutch when ambient temperatures are below about 10° C (50° F) due to the pressure/temperature relationship of the refrigerant.

The A/C pressure transducer is diagnosed using a DRBIII (R) scan tool.

The A/C pressure transducer cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.