This signal indicates to the PCM, that an A/C mode is selected at the A/C controller. The PCM uses this information to adjust the idle speed before turning on the A/C clutch. If this signal is not available to the PCM, the A/C compressor will be inoperative.

The A/C Request Signal (10) is a Class II Communication provided to the BFC and sent to the PCM through the Class II Communication circuit

Under normal operating conditions, the following actions occur:

1. The PCM supplies a ground to the relay coil of the A/C compressor control.
2. The relay energizes.
3. Voltage is supplied to the A/C compressor clutch through the relay center fuse.
4. The A/C compressor clutch engages.
5. The compressor runs.

If the PCM determines that the engine load should be reduced, such as during full throttle conditions, the PCM de-energizes the relay of the A/C compressor control in order to disengage the compressor clutch. The de-energization occurs even though the voltage signal from the heater and A/C control is still present at the PCM.

The electronic A/C refrigerant pressure sensor is mounted to the line between the condenser and the evaporator. The output to the PCM is variable and depends on the pressure inside the line. A higher pressure will result in a higher voltage out.

The PCM constantly monitors the A/C system pressure in order to achieve the following effects:

A fault in the A/C refrigerant pressure sensor signal will cause DTC P0530 to set.

For more information concerning A/C operation refer to Body Control System Operation in Body Control System, HVAC Compressor Controls Circuit Description in HVAC Systems -- Manual.