Part 1 of 2

Chart C-10 - A/C Clutch Control Circuit Diagnosis (Part 1 Of 2):

Chart C-10 Wiring Circuit:

Circuit Description:

The A/C clutch control relay is energized when the ECM provides a ground path through CKT 459 and A/C is requested. A/C clutch is delayed about .3 second after A/C is requested. This will allow the IAC to adjust engine RPM for the additional load.

The ECM will temporarily disengage the A/C clutch relay for a calibrated time for one or more of the following conditions:

^ Hot engine restart.
^ Wide open throttle (throttle angle over 90%).
^ Power steering pressure high.
^ Engine coolant temperature over 119°C (246°F).
^ During IAC reset.

The A/C clutch relay will remain disengaged when DTC 66 is present or there is no A/C request signal due to an open A/C select switch, or if the ECM detects high or low refrigerant pressure.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1 Determines whether or not the ECM is receiving an A/C request from the control head.
2. Determines whether or not the ECM is attempting to turn the A/C relay "ON."

Diagnostic Aids:

If complaint is insufficient cooling, the problem may be caused by an inoperative cooling fan. For cooling fan diagnosis, See Chart C-12, Cooling Fan Functional Check. If fan operates correctly, see "A/C Diagnosis" section.