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

CIRCUIT DESCRIPTION
The A/C clutch control relay is Engine Control Module (ECM) controlled to delay A/C clutch engagement 0.4 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.

CHART TEST DESCRIPTION
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.