Cooling Fan Electronic Control Unit (SC400)
- Disconnect Cooling Fan Electronic Control Unit (ECU) wiring harness connector. Using a voltmeter, measure voltage between connector terminal No. 1 and ground. See Fig 1. Battery voltage should be present.
- Turn ignition off. Using an ohmmeter, measure resistance between remaining connector terminals. See ECU CIRCUIT RESISTANCE SPECIFICATIONS table. Repair or replace as necessary.
ECU CIRCUIT RESISTANCE SPECIFICATIONS
| ECU Terminals | Condition | Ohmmeter Reading |
|---|---|---|
| 2 & 3 | Solenoid Valve 77°F (25°C) | 7.5-8.5 Ohms |
| 4 & GND | ----- | Continuity |
| 5 & GND | Throttle Valve Open | No Continuity |
| 5 & GND | Throttle Valve Closed | Continuity |
| 8 & GND | A/C Switch Disconnected | No Continuity |
| 8 & GND | A/C Switch Connected | Continuity |
| 9 & 10 | Eng. Temp. 177°F (80°C) | 1480-1580 Ohms |