Part 2 of 2

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

A/C Clutch Control Wiring Circuit (Rear A/C Option Only):

Circuit Description:

The A/C clutch control relay is ECM controlled to delay A/C clutch engagement about 8 seconds after engine is turned "ON." This allows the IAC to adjust engine RPM, before the A/C clutch engages. The ECM also causes the relay to disengage the A/C clutch during Wide Open Throttle (WOT) or if engine is overheating. The A/C clutch control relay is energized when the ECM provides a ground path for CKT 459. The high pressure switch will open if A/C pressure exceeds about 440 psi (3034 kPa). Vehicles equipped with rear A/C option utilize a pressure cycling switch instead of a low pressure switch. A/C pressure cycling switch closes above 296 to 338 kPa (43 to 49 psi) opens below 124 to 151 kPa (18 to 22 psi).

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

1. Determines if the signal is reaching the ECM from the A/C control panel. Signal should only be present when the A/C mode or defrost mode has been selected.

Diagnostic Aids:

If complaint was insufficient cooling, the problem may be caused by a inoperative cooling fan(s), or A/C refrigerant fan request switch. The engine cooling fan(s) should turn "ON," when A/C pressure exceeds 200 psi (380 kPa) to open the switch, which causes the ECM to energize the cooling fan relay(s). For cooling fan diagnosis, see Coolant Fan Control Circuit. If fan operates correctly, see A/C and Heating section.