Chart C-10 A/C Compressor Clutch Control

With A/C on, alternator voltage is supplied to A/C power relay. This actuates A/C power relay, through low pressure switch, high pressure switch (Red), A/C clutch relay, and compressor.

If system refrigerant level is okay, low pressure switch will be closed, completing circuit through high pressure cut-off switch (Red) to the A/C request input wire.

A/C request input wire supplies voltage to A/C control relay and ECM terminal B8. ECM will wait about 1/2 second and then ground terminal A4. This will close A/C relay, allowing current to flow through the relay and Red/Yellow wire to engage compressor clutch.

Fig 1: Chart C-10 Schematic - Checking A/C Clutch Control

Courtesy of GENERAL MOTORS CORP.

Fig 2: Chart C-10 Flow Chart - Checking A/C Clutch Control

Courtesy of GENERAL MOTORS CORP.