Component Diagnostic Charts/Tests

Fig. 028 - WIRING DIAGRAM for Chart C-10A A/C Clutch Control. VIN S:

CHART C-10A, A/C CLUTCH CONTROL (2.8L)

The A/C clutch control relay is ECM controlled to delay A/C clutch engagement .4 seconds after A/C 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 WOT operation, when high power steering pressure is present, or engine is overheating. The A/C clutch control relay is energized when the ECM provides a ground path for CKT 905.

Fig. 027 - Chart C-10A - A/C Clutch Control (1 of 2).:

1. Checks to see if ECM is controlling A/C clutch control relay.
2. Checks operation of A/C cycling switch.
3. Checks for grounded CKT 905 to ECM. At this point the test light should be off.
4. If the ECM recognizes a high power steering pressure signal, the A/C clutch relay will be de-energized. The ECM will pulse CKT 905 "on" and "off" to de-energize the relay. This would have caused a blinking light when CKT 905 was tested.

Fig. 028 - WIRING DIAGRAM for Chart C-10A A/C Clutch Control. VIN S:

CHART C-10B, A/C CLUTCH CONTROL (2.8L)

The A/C clutch control relay is ECM controlled to delay A/C clutch engagement .4 seconds after A/C 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 WOT operation, when high power steering pressure is present, or engine is overheating. The A/C clutch control relay is energized when the ECM provides a ground path for CKT 999.

Fig. 029 - Chart C-10B - A/C Clutch Control. VIN S:

1. Checks for battery voltage to relay through CKT 59.
2. Substitutes for relay to determine if problem is in relay or in CKT 59, A/C clutch coil, or ground.
3. Checks for open in CKT 59 between cycling switch and A/C fuse, or open CKT 59 to relay.
4. Checks to see that "A/C on" signal is getting to ECM through CKT 59. A test light off at this time indicates CKT 59 is open between the cycling switch and the ECM.