A/C Compressor

When the A/C compressor is activated, either by the ACC control module or by means of the A/C button on the dashboard, battery positive voltage (B+) is applied to pin 64 of the Motronic control module from the Integrated Central Electronics (ICE) module via the anti-frost thermostat and pressure switch.

The control module then opens the idle air control valve slightly more to prepare for the forthcoming load increase. After a short delay the control module grounds pin 48 which controls the A/C relay.

The engine control module breaks the circuit to pin 48 if the engine has not yet been started.