Component Diagnostic Charts/Tests

Chart C-10:

Wiring Diagram For A/C Clutch Control:

CIRCUIT DESCRIPTION:

When an A/C mode is selected on the A/C control switch, ignition voltage is supplied to the compressor low pressure switch. If there is sufficient system pressure, the low pressure switch will be closed and will complete the circuit to the high pressure cut-off switch and to circuits 603 and 604. The voltage on circuit 604 to the ECM is shown on the "Scan" tool as "ON" (voltage present) or "OFF" (no voltage). When a request for A/C is sensed by the ECM, the ECM will ground circuit 459 of the A/C clutch control relay. The relay will then send current to circuits 604 and 59 to engage the A/C compressor clutch. A "Scan" tool will display circuit 459 grounding by showing A/C clutch "ON." If the ECM sensed voltage from circuit 603, the cooling fan will be energized.


DIAGNOSTIC AIDS:

Both pressure switches are located at the rear of the A/C compressor. The low pressure switch connector can be identified by a blue insert and the high pressure switch connector by a red insert.