Massey Ferguson E977.05 – ECU: Engine Cooling Fan Speed Solenoid Issue

A malfunction in the electrical circuit or the physical operation of the solenoid responsible for controlling the variable speed of the engine's viscous cooling fan.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 4707
• 4708
• 4709
• 4710
• 5710SL
• 5711SL
• 5712SL
• 5713SL
• 7714
• 7715
• 7716
• 7718
• 7719
• 7720
• 7722
• 7724
• 7726

1. 1

   Trace the wiring harness from the Engine ECU to the cooling fan speed solenoid. Look for chafed wires, melted insulation, or breaks, particularly near hot engine components or moving belts.

2. 2

   Disconnect the plug at the fan solenoid. Inspect for water ingress, corrosion, or bent pins. Clean with contact cleaner if necessary.

3. 3

   Use a multimeter to measure the resistance across the solenoid coil pins. An open circuit (infinite resistance) or a dead short indicates a failed solenoid internally.

4. 4

   Back-probe the connector to ensure the ECU is sending the correct voltage/PWM (Pulse Width Modulation) signal to the solenoid when the engine reaches operating temperature.

1. 1

   Preparation

   Turn off the tractor, remove the key, and allow the engine to cool completely to avoid burns from the radiator or engine block.

2. 2

   Access the Fan

   Open the hood and remove any fan shrouds or guards blocking access to the engine cooling fan.

3. 3

   Disconnect Electricals

   Unplug the electrical connector leading to the fan speed solenoid.

4. 4

   Remove the Fan Assembly

   Relieve tension on the engine drive belt and slip it off the fan pulley. Unbolt the fan blades from the clutch assembly, then unbolt the viscous fan clutch/solenoid assembly from the water pump or mounting hub.

5. 5

   Replacement

   If the solenoid is available as a standalone part for your specific model, unbolt it from the clutch and replace it. Otherwise, install the new complete viscous fan clutch assembly.

6. 6

   Reassembly

   Reattach the fan blades, mount the assembly back onto the hub, and reinstall the drive belt, ensuring proper tension.

7. 7

   Reconnect and Test

   Plug the electrical connector back in. Clear the E977.05 fault code using a diagnostic tool, start the tractor, and bring it up to operating temperature to ensure the fan engages correctly and the code does not return.