Component Diagnostic Charts/Tests

Chart C-10A - A/C Clutch Control (Part 1 of 2):

Wiring Diagram for Chart C-10A - A/C Clutch Control:

CHART C-10A - A/C CLUTCH CONTROL (PART 1 OF 2)

Circuit Description:


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, when high power steering pressure is present, or if engine is overheating. The A/C clutch control relay is energized when the ECM provides a ground path for CKT 905.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if ECM is controlling A/C clutch control relay. If the ECM is in control of the clutch, there will be about a one half second delay.

1A. If the signal is present at "B8" with A/C "ON," and the clutch engages with the diagnostic terminal grounded, the A/C system is functional.

2. With the engine not running, the ECM should not turn "ON" the A/C clutch, unless the diagnostic terminal is grounded.


3. Checks operation of A/C cycling switch.


4. Checks for grounded CKT 905 to ECM. At this point, the test light should be "OFF."


5. If the ECM recognizes a high power steering pressure, the A/C clutch relay will be deenergized. The ECM will pulse CKT 905 "ON" and "OFF" to de-energize the relay. This would cause a blinking test light, when CKT 905 was tested.

Chart C-10A - A/C Clutch Control (Part 2 of 2):

CHART C-10A - A/C CLUTCH CONTROL (PART 2 OF 2) CONTINUED FROM CHART C-10A


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

6. Checks for battery voltage to relay through CKT 59.

7. Substitutes for relay to determine if problem is in relay or in CKT 59, A/C clutch coil, or ground.

8. Checks for open in CKT 59 between cycling switch and A/C fuse, or open CKT 59 to relay.


9. 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.