John Deere 000647.06 – ECU: Engine Cooling Fan Circuit Malfunction

The Engine Control Unit (ECU) has detected an electrical issue with the variable speed engine cooling fan circuit. This indicates a potential problem with the electrical supply or operation of the fan motor. On 5E Series tractors, this points to an output voltage issue (high/low voltage, open, or short circuit) in the cooling fan solenoid circuit. On 6M Series tractors, it specifically indicates an excessive current draw (high amps) from the intercooler hydraulic fan drive solenoid.

• 5085E
• 5085M
• 5090E
• 5090EL
• 5100E
• 6110M
• 6120M
• 6130M
• 6R

1. 1

   Visually inspect the wiring harness and connectors leading to the cooling fan solenoid for chafing, melted insulation, corrosion, or loose connections. Perform a wiggle test to identify intermittent faults

2. 2

   With the key on, back-probe the solenoid connector to confirm it is receiving the correct supply voltage and has a solid ground connection, checking for voltage drops

3. 3

   Disconnect the solenoid and measure the resistance across its coil terminals using a multimeter. A very high reading indicates an open coil, while a near-zero reading suggests a shorted coil. For some 12V fan clutch solenoids, test if typical current draw is between 1.0 and 2.0 Amps

4. 4

   For hydraulically controlled fans, check for low hydraulic oil levels and inspect the hydraulic filter for debris, which could indicate a fan valve problem

5. 5

   Perform a default to full speed test by unplugging the fan solenoid. If the fan runs at full speed as a fail-safe, the issue is likely in the electrical control circuit rather than the hydraulic motor

1. 1

   Isolate the fault and repair wiring

   If a wiring issue is found during inspection, repair the damaged section with solder and heat-shrink tubing, then secure the harness away from potential damage points. Clean corroded terminals and apply dielectric grease.

2. 2

   Replace solenoid coil or valve

   If the solenoid coil tests out of specification (open, shorted, or high current draw), replace the coil. If the entire solenoid valve is faulty, replace the complete valve assembly.

3. 3

   Clear fault codes

   After completing the repair, clear the diagnostic trouble codes from the ECU.

4. 4

   Verify repair

   Operate the machine under normal conditions to ensure the cooling fan functions correctly and the fault code does not reappear.