Chart C-12H Coolant Fan Check (With Dual Fans)
Chart C-12H - Coolant Fan Check With Dual Fans:
Wiring Diagram for Chart C-12H - Coolant Fan Check With Dual Fans:
CHART C-12H - COOLANT FAN CHECK (WITH DUAL FANS) PART 1 OF 3
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1. Checks to see if fans run 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 150 W fan should run.
3. Grounding the coolant temperature override switch harness to ground should cause the relays to turn "ON" both fans. If the fans run, the fan control relays and CKT 335 to the coolant temperature override switch are good.
4. Grounding each pressure switch terminal should cause relays to close, turning "ON" fans, proving relays and circuits 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 timer relay works. With coolant temperature override switch harness grounded and ignition "OFF," 150 W fan should run about 10 minutes or until ground jumper is removed.
Chart C-12I - Coolant Fan Check - With Dual Fans (Part 2 of 3):
CHART C-12I - COOLANT FAN CHECK (WITH DUAL FANS) PART 2 OF 3 - CONTINUED FROM CHART C-12H
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
7. This check bypasses the relay and applies BATT + 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 BATT + 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-12J - Coolant Fan Check - With Dual Fans (Part 3 of 3):
CHART C-12J - COOLANT FAN TIMER CHECK (WITH DUAL FANS) PART 3 OF 3 - CONTINUED FROM CHART C-12H
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
12. Checks to be sure constant BATT + is at terminals "1 and 2" to the timer relay.
13. Checks to be sure CKT 639 does not 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-12K - Coolant Fan Always On With Dual Fans:
CHART C-12K - COOLANT FAN ALWAYS ON (WITH DUAL FANS)
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 or 533.
17. Checks to see if CKT 335 or 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 both fan control relays. Replace, if resistance is less than 20 ohms. Also, be sure that CKT 535 is not shorted to BATT+, and check the resistance of the canister purge solenoid and replace, if under 20 ohms.