A/C Compressor

When the A/C compressor is activated, either from the ACC engine control module or by means of the A/C button on the dashboard, current (B+) is applied to pin 59 of the Trionic engine control module via Integrated Central Electronics (ICE), the antifrost thermostat and the pressure switch.

The engine control module then opens the idle air control valve slightly wider to prepare for the forthcoming load increase. After a short delay the engine control module grounds pin 54, which is connected to the A/C relay.

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