Grand Caravan V6-3.8L (2009)
Refrigerant Pressure Sensor / Switch: Description and Operation
Front A/C Pressure Transducer - Operation
OPERATION
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 receiver/drier.
The internal resistance of the A/C pressure transducer changes in response to the pressures it monitors. The Totally Integrated Power Module (TIPM)
provides a five volt reference signal and a sensor ground to the A/C pressure transducer. The TIPM then monitors the output voltage of the A/C pressure
transducer on a sensor return circuit to determine refrigerant pressure and sends a message to the Powertrain Control Module (PCM) or the Engine
Control Module (ECM) (depending on engine application). The PCM/ECM 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/ECM will disengage the A/C compressor clutch when high side pressure rises above 3082 kPa (447 psi) and re-engage the
clutch when high side pressure drops below 2937 kPa (426 psi). The A/C pressure transducer will also disengage the A/C compressor clutch if the high
side pressure drops below 110 kPa (16 psi) and will re-engage the clutch when the high side pressure rises above 221 kPa (32 psi). If the refrigerant
pressure rises above 1655 kPa (240 psi), the PCM/ECM will actuate the cooling fan. The A/C pressure transducer message to the PCM/ECM 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.
A Schrader-type valve in the receiver/drier fitting permits the A/C pressure transducer to be removed or installed without disturbing the refrigerant in the
A/C system.
The A/C pressure transducer is diagnosed using a scan tool See: Powertrain Management/Computers and Control Systems/Testing and
Inspection/Diagnostic Trouble Code Tests and Associated Procedures.
The A/C pressure transducer cannot be adjusted or repaired and must be replaced if inoperative or damaged.
