Case IH 3385 – Engine Control Unit (ECU): Viscous fan actuation driver solenoid circuit - open circuit or short to ground

The electrical path controlling the engine's cooling fan clutch is either broken (open circuit) or the wiring is making unintended contact with the machine's chassis (short to ground). As a result, the control module cannot properly regulate the fan speed, which can lead to engine overheating or overcooling.

• Steiger T4B
• STX Steiger
• Quadtrac
• STX375
• STX425
• STX430
• STX450
• STX500
• Steiger 370
• Steiger 380
• Steiger 385
• Steiger 430
• Steiger 485
• MX series
• Magnum
• 8930
• 8940
• 8950
• MX210 through MX285

1. 1

   Inspect the electrical connectors at both the viscous fan drive solenoid and the Engine Control Unit (ECU). Ensure the connectors are fully seated, not damaged, and that the pins are tight and free of corrosion.

2. 2

   Disconnect the harness and use a multimeter to test the wiring between the fan solenoid and the ECU for continuity to rule out a broken wire (open circuit).

3. 3

   Test the harness wires for continuity to the chassis ground. If continuity is found where there shouldn't be, there is a short to ground in the harness.

4. 4

   Test the internal resistance of the viscous fan solenoid itself to see if the internal coil has failed (shorted or opened).

1. 1

   Turn off the tractor and disconnect the battery

   Ensure safety before beginning the repair.

2. 2

   Disconnect the solenoid electrical connector

   Locate the viscous fan drive assembly at the front of the engine and disconnect the solenoid electrical connector.

3. 3

   Disconnect the corresponding connector at the Engine Control Unit (ECU)

   Disconnect the ECU connector to isolate the harness.

4. 4

   Perform multimeter checks on the wiring harness

   If a short or break is found in the wiring, locate the chafed or broken section and repair the damaged wiring (or replace the harness section).

5. 5

   Replace the defective solenoid or the entire viscous fan clutch assembly

   If the wiring harness tests perfectly fine, the fault lies within the viscous fan drive solenoid. Depending on the specific fan drive model, either replace the defective solenoid using a solenoid service kit, or replace the entire viscous fan clutch assembly.

6. 6

   Reconnect all electrical connectors and the battery

   Ensure all connections are secure.

7. 7

   Clear the fault code from the ECU

   Connect the Electronic Service Tool (EST) to clear the fault code from the ECU.

8. 8

   Verify the repair

   Start the engine, bring it to operating temperature, and verify that the fan engages properly and the fault code does not return.