A/C Signal: Description and Operation

These input signals indicate to the ECU that air conditioning switch is in the ON position, and that a signal needs to be sent to the air conditioning clutch relay to engage the compressor clutch. Before the A/C clutch can be engaged, the ECU will increase the engine speed to ensure that the added load of the A/C compressor will not kill the engine.

The ECU increases the idle through both the A/C select and A/C request controls. The ISA motor is extended via the A/C select circuit, and the injector pulse width is increased via the A/C request circuit.