Chart C-10, 3.1L, A/C Clutch CTRL CKT Diagnosis: Notes

A/C relay is ECM controlled to delay A/C clutch engagement .4 second after A/C is turned on. This allows IAC motor to adjust engine RPM before A/C clutch engages. ECM also causes relay to disengage A/C clutch during WOT operation. A/C relay is energized when ECM provides ground to circuit No. 459.

1. ECM will only energize relay when engine is running. This test will determine if relay or circuit No. 459 is faulty.
2. To engage compressor clutch, the pressure cycling switch must be closed to provide 12 volts to the relay, and the high pressure switch must be closed, so that A/C request (12 volts) will be present at ECM.
3. Determines if signal is reaching ECM on circuit No. 366 from A/C control panel. Signal should only be present when A/C or defrost mode has been selected.
4. This step checks for a short to ground in any part of the A/C request circuit, circuit No. 67 to relay, circuit No. 59 to A/C clutch, or a shorted A/C clutch unit.
5. If ECM sees a high power steering pressure signal, ECM will disengage A/C clutch.
6. With engine idling and A/C on, ECM should be grounding circuit No. 459, which should cause test light to illuminate.