RAM 2500 Truck 2WD V8-5.7L VIN D (2004)
Refrigerant Pressure Sensor / Switch: Description and Operation
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 condenser
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 discharge 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 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 discharge line. The
transducer will change its internal resistance in response to the pressures it monitors. The Powertrain Control Module (PCM) or the Engine Control
Module (ECM) depending on engine application, 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/ ECM 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/ECM will also prevent the air
conditioning compressor clutch from engaging when ambient temperatures are below about 10° C (50° F) 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 DRBIII(R) scan tool. Refer to the appropriate diagnostic information.
