TRANSDUCER-A/C PRESSURE
DESCRIPTION
The A/C pressure transducer (1) is a switch that is installed on a fitting located on the A/C discharge line. An internally threaded fitting on the A/C pressure transducer connects it to the externally threaded Schrader-type fitting on the A/C discharge line. A rubber O-ring seals the connection between the A/C pressure transducer and the discharge line fitting. The A/C pressure transducer is connected to the vehicle electrical system by a molded plastic connector with three terminals.
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 swashplate within the A/C compressor and the radiator cooling fan to help optimize A/C system performance and to protect the system components from damage. The PCM adjusts the swashplate to nearly a zero degree angle (low compressor displacement) when high side pressure rises above 3130 kPa (454 psi) and re-adjusts the swashplate to a greater angle (higher compressor displacement) when high side pressure drops below 1999 kPa (290 psi). The A/C pressure transducer also reduces the swashplate angle if the high side pressure drops below 200 kPa (29 psi) and will increase the swashplate angle when the high side pressure rises above 234 - 262 kPa (34 - 38 psi). When the refrigerant pressure rises above 1655 kPa (240 psi), the PCM will actuate the cooling fan.
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. Refer to 9 - Engine Electrical Diagnostics for more information.
The A/C pressure transducer cannot be adjusted or repaired and, if faulty or damaged it must be replaced.
REMOVAL
NOTE: It is not necessary to discharge the refrigerant system to replace the A/C pressure transducer.
NOTE: Typical A/C pressure transducer shown.
1. Disconnect and isolate the negative battery cable.
2. Remove the upper radiator closure panel and carefully pull the top of the fascia forward to gain access to the A/C pressure transducer (2) (refer to 23 - BODY/EXTERIOR/CLOSURE PANEL-UPPER RADIATOR - REMOVAL).
3. Reach down through the opening between the A/C condenser and the front fascia and disconnect the wire harness connector (1) from the A/C pressure transducer located on the A/C discharge line (3).
4. Remove the A/C pressure transducer from the fitting on the A/C discharge line and remove and discard the O-ring seal.
INSTALLATION
NOTE: Use only the specified O-ring as it is made of special material for R-134a. Use only refrigerant oil of the type required for the A/C compressor.
NOTE: Typical A/C pressure transducer shown.
1. Lubricate a new rubber O-ring seal (4) with clean refrigerant oil and install it onto the discharge line fitting (3).
2. Install the A/C pressure transducer (2) onto the A/C discharge line. Tighten the A/C pressure transducer securely.
3. Connect the wire harness connector (1) to the A/C pressure transducer.
4. Install the upper radiator closure panel (refer to 23 - BODY/EXTERIOR/CLOSURE PANEL-UPPER RADIATOR - INSTALLATION).
5. Reconnect the negative battery cable.