A/C Request Signal

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 is a battery positive voltage that is supplied to the PCM when the A/C control is activated or when the Heater-A/C control mode selector is placed in any of the following modes:
^ MAX A/C
^ NORM A/C
^ BI-LEVEL
^ DEFOG
^ DEFROST

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.