A/C Compressor

When the A/C compressor is activated, either from the ACC control module or by means of the A/C button on the dashboard, positive battery voltage (B+) is applied to pin 59 of the Trionic control module via the EDU, antifrost thermostat and pressure switch.

The control module then opens the idle air control valve slightly wider to prepare for the forthcoming load increase. After a short delay the 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.