Operation

OPERATION

The rear A/C pressure transducer monitors the pressures in the high side of the rear refrigerant system through its connection to the rear liquid line at the rear A/C receiver/drier. The rear A/C pressure transducer will change its internal resistance in response to the pressures it monitors.

The front control module (FCM) provides a five volt reference signal to the rear A/C pressure transducer, then monitors the output voltage of the pressure transducer on a sensor return circuit to determine rear refrigerant system pressure. The FCM broadcasts a rear refrigerant pressure message to the powertrain control module (PCM) or the engine control module (ECM) (depending on engine application) which is programmed to respond to the rear A/C pressure transducer and other sensor inputs by controlling the operation of the rear A/C compressor clutch and the rear condenser cooling fans to help optimize rear A/C system performance and to protect the rear refrigerant system components from damage. The PCM/ECM will disengage the rear A/C compressor clutch when high side pressure rises above 3275 kPa (475 psi) and re-engage the clutch when high side pressure drops below 1999 kPa (290 psi). The PCM/ECM will also disengage the rear 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 rear refrigerant system pressure rises above 1655 kPa (240 psi), the PCM/ECM will actuate the rear condenser cooling fans. The rear A/C pressure transducer message to the PCM/ECM will also prevent the rear 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. Refer to the Electric A/C Condenser Cooling Fan Switch Point chart for condenser cooling fan on/off pressures.

The rear A/C pressure transducer is diagnosed using a scan tool.

The rear A/C pressure transducer cannot be adjusted or repaired and must be replaced if inoperative or damaged.