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Chart C-10 A/C Clutch Control Circuit Diagnosis:

A/C Clutch Control Schematic:

CIRCUIT DESCRIPTION
The A/C clutch control relay is Powertrain Control Module (PCM) controlled to delay A/C clutch engagement about 8 seconds after engine is turned "ON." This allows the Idle Air Control (IAC) to adjust engine RPM, before the A/C clutch engages. The PCM 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 PCM provides a ground path for CKT 459. The low pressure switch will open if A/C pressure is less than 40 psi (276 kPa). 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). An A/C refrigerant fan request switch opens to request the fan(s) "ON," when A/C pressure exceeds about 200 psi (1380 kPa).

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. The PCM will only energize the A/C relay, when the engine is running. This test will determine if the relay or CKT 459 is faulty.
2. Determines if the signal is reaching the PCM on CKT 66 from the A/C control panel. Signal should only be present when the A/C mode or defrost mode has been selected.
3. With the engine idling and A/C "ON," the PCM should be grounding CKT 459, which should cause the test light to be "ON."

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 a value to open the switch, which causes the PCM to energize the cooling fan relay(s). See Chart C-12 Coolant Fan Control Circuit under C Charts, for cooling fan diagnosis. Chart C-12 Coolant Fan Control Circuit