Transducer-A/C Pressure: Operation

WARNING: This page is about a different car, the 2005 Dodge Durango. However, it is still accessible from the selected car via links, so may be relevant.

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 A/C pressure transducer will change its internal resistance in response to the pressures it monitors. A 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 A/C system.

The front control module (FCM) provides a five volt reference signal to the A/C pressure transducer, then monitors the output voltage of the A/C pressure transducer on a sensor return circuit to determine refrigerant pressure. The FCM broadcasts a refrigerant pressure message to the PCM, which is programmed to respond to the A/C pressure transducer 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 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 message to the PCM 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. Refer to ELECTRIC A/C CONDENSER COOLING FAN SWITCH POINT table for condenser cooling fan on/off pressures.

The A/C pressure transducer cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The A/C pressure transducer is diagnosed using a scan tool. Refer to appropriate Engine ELECTRICAL DIAGNOSTICS article for more information.

ELECTRIC A/C CONDENSER COOLING FAN SWITCH POINT

Fan State	Switch Point
Off to Low speed	1896 kPa (275 psi)
Low to High speed	2103 kPa (305 psi)
High to Low speed	1620 kPa (235 psi)
Low speed to Off	1344 kPa (195 psi)
Off to Low, Low to Off hysteresis	5552 kPa (80 psi)
Low to High, High to low hysteresis	483 kPa (70 PSI)