RAM 3500 HD Truck 2WD L6-6.7L DSL Turbo (2008)
Refrigerant Pressure Sensor / Switch: Description and Operation
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 discharge line
and its internal resistance changes 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 A/C pressure 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 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 3172 kPa (460 psi) and
re-engage the clutch when high side pressure drops below 1999 kPa (290 psi). The A/C pressure transducer will also disengage the A/C compressor
clutch if the high side pressure drops below 193 kPa (28 psi) and will re-engage the clutch when the high side pressure rises above 234 kPa (34 psi). If
the refrigerant pressure rises above 1655 kPa (240 psi), the PCM will actuate the cooling fan. The A/C pressure transducer signal to the PCM/ECM also
prevents the A/C compressor clutch from engaging when ambient temperatures are below about 10° C (50° F) due to the pressure/temperature
relationship of the refrigerant.
A Schrader-type valve in the A/C discharge line 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.
The A/C pressure transducer cannot be adjusted or repaired and must be replaced if found inoperative or damaged.
