Chart C-10, 4.3L A/C Clutch CTRL CKT Diagnosis
When A/C switch is turned on, ignition voltage is supplied to the pressure cycling switch through the control head. If there is a sufficient A/C charge, the pressure cycling switch will be closed to complete the circuit to the ECM and to the A/C high pressure switch. If A/C head pressure is not too high, circuit would be completed to the A/C clutch coil.
NOTE:
Test numbers refer to test numbers on diagnostic charts.
- Checks for short to ground in circuits No. 66, No. 67 or No. 1592, if fuse was open. Check for shorted compressor clutch coil. Check A/C system for further diagnosis of power feed circuit to the control head.
- Check to determine if ECM is capable of detecting A/C status.
- If A/C clutch engaged, check for 12 volt supply at ECM terminal B8. If voltage is present, a faulty connection exists at the ECM or ECM is faulty.
- Before replacing control head, perform thorough A/C system diagnosis.