Operation and AC Compressor

When the AC compressor is activated, either from the ACC or using the AC button on the facia, the Trionic ECM receives Batt+ on pin 59.

The ECM then opens the [1][2]idle air control valve slightly more to prepare for the imminent increase in load. After a short delay, the ECM grounds pin 54, which is connected to the AC relay via the pressure switch.

The ECM breaks the circuit to pin 54 if the engine has not yet been started.