Part 1 of 2

Chart C-10 Part 1 Of 2:

Chart C-10 Wiring Diagram:

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. The A/C clutch is delayed about 0.3 seconds 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 calibrated times for one or more of the following:

^ Hot engine restart.
^ Wide open throttle (TPS over 90%).
^ Engine rpm greater than about 6000 rpm.
^ During IAC reset.

The A/C clutch will remain disengaged when a Code 66 is present and if pressure is out of range or there is no A/C request signal due to an open A/C select switch or circuit. Also if the ECM detects high or low refrigerant pressure it will disengage the A/C compressor clutch.


TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Determines whether of 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.