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CIRCUIT DESCRIPTION:

The A/C clutch control relay is controlled by the ECM to delay clutch engagement for approximately 0.4 seconds after the A/C system is powered. This allows the ECM to adjust engine speed before the A/C clutch engages. The ECM also disengages the A/C clutch during Wide Open Throttle (WOT) operation.

When the A/C selector control is switched to the "ON" position, ignition voltage is supplied to the pressure cycling switch. If there is sufficient A/C charge, the pressure cycling switch will be closed to complete the circuit to the ECM and A/C clutch control relay.

When the A/C request signal is received by the ECM, the ECM will ground relay circuit 459 long enough to adjust the engine idle speed. Once the idle speed has been adjusted, the ECM will remove the ground from the relay circuit 459. This will allow current to flow through the relay and to the A/C compressor clutch.


TEST DESCRIPTION:


1. Confirms 12 volt supply to the A/C control relay. The A/C control relay is located in the convenience center. (relay "C") C-68 option only.

2. Jumpering the harness connector will determine if the high side pressure cutoff switch is open.