Chart C-10, 2.5L, A/C Clutch CTRL CKT Diagnosis: Notes

A/C clutch control is ECM controlled. ECM delays A/C clutch engagement approximately .4 second after A/C is turned on. This allows Idle Air Control (IAC) to adjust engine RPM before clutch engages. ECM also disengages A/C clutch during Wide Open Throttle (WOT), when high power steering pressure is present, or if engine is overheating. A/C clutch relay is energized when ECM provides a ground for circuit No. 459. A/C low pressure switch will open if A/C pressure is less than 40 psi (2.8 kg/cm² ). A/C high pressure switch will open if A/C pressure exceeds 440 psi (30.9 kg/cm² ). A/C compressor/engine cooling fan temperature switch (if equipped) opens when A/C pressure exceeds approximately 250 psi (17.6 kg/cm² ). Cooling fan No. 2 will then turn on.

1. ECM will only energize A/C relay when engine is running. Determines if relay or circuit No. 459 is faulty.
2. For clutch to properly engage, low pressure switch must be closed to provide battery voltage to relay. High pressure switch must be closed, so A/C request (B+) will be present at ECM.
3. Determines if signal is reaching ECM from circuit No. 66 from A/C control panel. Signal should only be present when A/C mode or defrost mode is selected.
4. Short to ground in any part of A/C request circuit could cause a blown fuse.
5. With engine idling and A/C on, ECM should ground circuit No. 459, which should cause test light to glow.