A/C Signal: Description and Operation

AIR CONDITIONING PRESSURE TRANSDUCER-PCM INPUT
The Powertrain Control Module (PCM) monitors the A/C compressor discharge (high side) pressure through the air conditioning pressure transducer. The transducer supplies an input to the PCM. The PCM engages the A/C compressor clutch if pressure is sufficient for A/C system operation.

Fig 20 Power Distribution Center (PDC):

AIR CONDITIONING COMPRESSOR CLUTCH RELAY-PCM OUTPUT
The Powertrain Control Module (PCM) operates the air conditioning clutch relay ground circuit. The battery supplies power to the solenoid side of the relay. The PCM grounds the relay when the operator puts the A/C or defrost switch in the ON position and it receives an acceptable input from the A/C pressure transducer. If the A/C pressure transducer input indicates high side pressure is too high or too low, the PCM will not ground the A/C compressor clutch relay.

With the engine operating, the PCM cycles the air conditioning clutch on and off during A/C operation. When the PCM senses low idle speeds or wide open throttle through the throttle position sensor, it de-energizes the A/C compressor clutch relay.

The A/C compressor clutch relay is located in the Power Distribution Center (PDC) (Fig. 20). A decal on the inside of the PDC covers shows the locations of each relay and fuse contained in the PDC.