Kubota E:025 – Main ECU: Battery Overcharging

The system triggers this warning when it detects that the power supply voltage has exceeded 18 Volts. This condition is typically caused by external user error (the machine was incorrectly jump-started using a 24-Volt battery, or a 24V battery was mistakenly installed in the 12V system) or component failure (the alternator's internal voltage regulator has failed, causing the alternator to run unregulated and overcharge the 12V electrical circuit).

• U-17
• U25
• U35
• U50-5
• U50-5S
• U55-4
• KX015-4
• KX030-4
• KX057-4
• KX080-3
• KX080-3S
• KX161-3

1. 1

   Perform a visual battery check to verify the machine is not currently hooked up to a 24V jump-starter and that a standard 12V battery is installed.

2. 2

   Use the Meter Panel Tester Mode: Turn the key switch to the ON position (engine stopped) and verify the panel reads approximately 12.0 V. Start the engine and verify it reads approximately 14.0 V to 14.5 V. If the warning lamp illuminates and displays E:025, proceed to the next step.

3. 3

   Perform an alternator voltage output test: With the engine running, use a multimeter to measure the voltage directly between Terminal B on the alternator and a solid body ground (GND). If the multimeter reads over 18 V, the alternator's voltage regulator has failed.

1. 1

   Disconnect Power

   Turn the key switch to 'STOP'. Disconnect the negative battery cable first, followed by the positive cable, to prevent electrical arcing or further damage to the Main ECU.

2. 2

   Disconnect Alternator Wiring

   Disconnect the wiring harness connector and the Terminal B wire from the back of the alternator.

3. 3

   Remove the Belt

   Loosen the alternator mounting bolts and the tensioner bracket. Push the alternator inward to relieve tension on the fan/alternator V-belt, then slip the belt off the pulley. (Inspect the belt for glazing or cracking; replace if necessary).

4. 4

   Remove the Alternator

   Remove the mounting hardware completely and extract the faulty alternator from the engine bay.

5. 5

   Install the New Alternator

   Position the new alternator and loosely install the mounting bolts.

6. 6

   Tension the Belt

   Route the V-belt over the new alternator pulley. Use a pry bar to apply tension to the alternator until the belt deflection meets Kubota's specification (usually about 7-9mm of deflection under 10kg of force), then tighten the mounting bolts securely.

7. 7

   Reconnect Wiring

   Reattach the Terminal B wire and plug in the alternator harness connector.

8. 8

   Reconnect Battery

   Reconnect the positive battery cable, followed by the negative cable.

9. 9

   Verify Repair

   Start the engine and check the LCD Meter Panel. Ensure the voltage reads ~14.0V - 14.5V and the E:025 code has cleared.