John Deere 000647.03 – ECU: Fan Solenoid Output Voltage High

The Engine Control Unit (ECU) has detected a higher than normal voltage in the electrical circuit for the variable speed engine cooling fan solenoid. This indicates a potential short circuit to a power source or a malfunctioning solenoid, which can disrupt the Pulse Width Modulated (PWM) signal and cause the cooling fan to run at an incorrect speed or not at all.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 8R Series
• K-Series Loaders

1. 1

   Access the diagnostic menu, record all active and stored fault codes, and clear them to see if 000647.03 immediately returns

2. 2

   Visually inspect the wiring harness leading to the variable speed fan solenoid for signs of damage, chafing, melting, or corrosion on the connectors

3. 3

   Perform a solenoid resistance check: Disconnect the fan solenoid and measure resistance between its pins. Typical resistance is 27-30 ohms; readings significantly outside this range indicate a faulty solenoid

4. 4

   Perform a short circuit check: With the solenoid disconnected and ignition on (engine off), check for voltage at the solenoid connector. Any voltage present indicates a short to a power source within the wiring harness

1. 1

   Repair or replace wiring harness

   If diagnostic checks reveal a short circuit to a power source or physical damage to the wiring harness, repair or replace the affected sections and ensure all connections are clean and secure.

2. 2

   Replace fan solenoid

   If the solenoid's resistance is outside the 27-30 ohm specification, replace the variable speed fan solenoid valve.

3. 3

   Verify repair

   Clear all diagnostic trouble codes, operate the machine, and verify that the cooling fan operates as expected without the fault returning.