A/C Clutch Circuit Operation

A/C Clutch Circuit Operation
A 12-volt signal is supplied to the A/C request input of the ECM when the A/C is selected through the A/C control switch.

The A/C compressor clutch relay is controlled through the ECM. This allows the ECM to modify the idle air control position prior to the A/C clutch engagement for better idle quality. If the engine operating conditions are within their specified calibrated acceptable ranges, the ECM will enable the A/C compressor relay. This is done by providing a ground path for the A/C relay coil within the ECM. When the A/C compressor relay is enabled, battery voltage is supplied to the compressor clutch coil.

The ECM will enable the A/C compressor clutch whenever the engine is running and the A/C has been requested. The ECM will not enable the A/C compressor clutch if any of the following conditions are met:

- The throttle is greater than 72% for 1.0 second.
- The engine speed is greater than 6500 RPM.
- The ECT is greater than 117 °C (246 °F).
- The elapsed time after engine starts is less than 3 seconds.