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Chart C-10, 3.4L (1 Of 2), A/C Clutch Control CKT Diagnosis: Notes

The A/C clutch control relay is ECM controlled to delay A/C clutch engagement about .4 second after A/C is turned on. This allows IAC to adjust engine RPM, before clutch engages. The ECM also disengages the A/C clutch during WOT, when high power steering pressure is present, or if engine is overheating. The A/C clutch control relay is energized when the ECM provides a ground path for circuit No. 459. The A/C pressure sensor is used to determine high or low pressure in the system and also turns on the cooling fan when needed.

NOTE: Test numbers refer to test numbers on diagnostic charts.
  1. ECM will only energize A/C relay when engine is running. This test determines if relay or circuit No. 459 is faulty.
  2. This test determines if signal is reaching ECM on circuit No. 66 from A/C control panel. Signal should only be present when A/C or defrost mode has been selected.
  3. If ECM sees a high power steering pressure signal, ECM will disengage A/C clutch.
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