General Information

The purpose of the Air Conditioning (A/C) system is to provide cool air and remove humidity from the interior of the vehicle. The A/C system is engaged when the HVAC control module (IPM) is in any mode. The A/C system can operate regardless of the temperature setting, as long as outside ambient temperature is above 3°C (37°F). The vehicle passenger and back seat passengers can adjust the temperature offset by adjusting the right air temperature switch. The back seat passengers can adjust the temperature offset by adjusting the auxiliary temperature switch. Both the passenger and back seat temperatures can be set 4°C (7°F) cooler or warmer than the drivers setting.

The IPM receives power from the rear fuse block through the ignition 3 voltage circuit. Ground is provided by the ground circuit.

When the A/C request is selected, a signal is sent from the IPM to the powertrain control module (PCM). In order for the PCM to internally ground the A/C clutch relay control circuit, the Dash Integration Module (DIM) and PCM must communicate with each other over the class 2 serial data circuits. The PCM monitors A/C refrigerant line pressure and engine coolant temperature. This information is placed on the class 2 serial data circuit and is monitored by the DIM. The DIM looks at the A/C line pressure, the A/C refrigerant low temperature sensor, engine coolant temperature, battery voltage along with the A/C request input from the HVAC control module. The DIM will request A/C operation from the PCM if these parameters are within normal operating limits and the IPM is requesting A/C operation. If there is a malfunction in the A/C system, the instrument panel will read SERVICE A/C SYSTEM to alert the vehicle operator that there is a malfunction with the A/C system. The PCM will engage the A/C clutch anytime the engine speed is below 5000 RPM and the A/C is requested unless any of the following conditions exists:
^ Throttle angle is 100 percent
^ A/C refrigerant pressure sensor detects a condition lower than 224 KPA (32 PSI)
^ A/C refrigerant pressure sensor detects a condition higher than 2968 KPA (49 PSI)
^ Low battery voltage
^ Engine Coolant Temperature (ECT) IS MORE THAN 121 C (25 F)

The PCM turns on the A/C compressor by providing a path to ground through the A/C clutch relay control circuit for the A/C compressor clutch relay. Power is provided to the A/C compressor clutch relay internally of the underhood fuse block. Once the relay closes its internal switch, power from the battery is provided to the A/C compressor clutch through the A/C compressor clutch supply voltage circuit. Whenever the compressor is turned off, the A/C compressor clutch diode provides a path for the voltage spike resulting from the collapsing magnetic field of the compressor clutch coil. The ground circuit provides a pathway to ground for the compressor. The A/C clutch relay control circuit is grounded internally within the PCM.