RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
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 refrigerant discharge line between the compressor and the
condensor in the front 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 discharge 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 take out 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 musty 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 discharge
line. The transducer will change its internal resistance in response to the pressures it monitors. The Powertrain 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 air
conditioning 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 air conditioning compressor clutch from engaging
when ambient temperatures are below about 10 °C due to the pressure/temperature relationship of the refrigerant. The 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 system. The A/C
pressure transducer is diagnosed using a DRB III scan tool. Refer to the appropriate diagnostic information.
