Chart C-12D Coolant Fan Check With A/C (Single Speed)
Chart C-12D - Coolant Fan Check With A/C (Part 1 of 3):
Wiring Diagram for Chart C-12D - Coolant Fan Check With A/C:
CHART C-12D - COOLANT FAN CHECK WITH A/C (SINGLE SPEED) PART 1 OF 3
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1. Checks to see if fan runs at all times with ignition "ON".
2. Grounding the "test" terminal in the ALDL connector should cause the ECM to ground CKT 535. At this point, the fan should run.
3. Grounding the coolant temperature override switch harness to ground should cause the relay to turn "ON" the fan. If the fan runs, the fan control relay and CKT 335 to the coolant temperature override switch are good.
4. Grounding high pressure switch terminal should cause relay to close, turning "ON" fan, proving relay and circuit are OK.
5. Checks to see if coolant temperature override switch operates correctly. Test light should come "ON" at about 108~C (226~F) and the hot light on the instrument panel should come "ON" above 116~C (241~F).
6. Checks to see if coolant fan delay relay works. With coolant temperature override switch harness grounded and ignition "OFF", fan should run about 10 minutes or until ground jumper is removed.
Chart C-12E - Coolant Fan Check With A/C:
CHART C-12E - COOLANT FAN CHECK WITH A/C (SINGLE SPEED) PART 2 OF 3 - CONTINUED FROM CHART C-12D
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
7. This check bypasses the relay and applies B+ direct to the fan through CKT 532. At this point, the fan should run.
8. Checks to see if problem is the control relay, wiring, or ECM.
9. Checks for presence of ignition voltage to relay connector terminal "5".
10. Checks for presence of B+ to relay connector terminal "1".
11. Check for an open ground or fan motor circuit, then checks for an open in CKT 532 between relay and motor or faulty motor.
Chart C-12F - Coolant Fan Check With A/C:
CHART C-12F - COOLANT FAN CHECK WITH A/C (SINGLE SPEED) PART 3 OF 3 - CONTINUED FROM CHART C-12D
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
12. Checks to be sure constant B+ is at terminals "1" and "2" to the timer relay.
13. Checks to be sure CKT 639 does not have ignition voltage, when the ignition switch is "OFF". If CKT 639 has battery voltage with the ignition "OFF", the timer relay will not turn the fan "ON".
14. Checks to be sure CKT 450 is a good ground.
Chart C-12G - Coolant Fan Always On:
CHART C-12G - COOLANT FAN ALWAYS ON WITH A/C - CONTINUED FROM CHART C-12D
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
15. This step will separate the problem between the timer relay or the fan control relay.
16. Checks for short to voltage in CKT 532.
17. Checks to see if CKT 535 is shorted to ground, which would keep the relay grounded at all times.
18. Checks to see if CKT 335 is shorted to ground. A light indicates the wire is shorted to ground and the following steps will isolate the short.
19. If the test light is "OFF" after disconnecting, the ECM is shorted internally. Before replacing the ECM, be sure and check the resistance value of the low speed fan control relay. Replace if resistance is less than 20 ohms. Also, be sure that CKT 535 is not shorted to B+, and check the resistance of the canister purge solenoid and replace if under 20 ohms.