John Deere 003353.14 – CCU: Alternator Not Charging CCU

The alternator is not providing a charge to the Main Control Module (CCU). The electrical system has detected that the alternator's output is insufficient to power the CCU and charge the battery. A healthy charging system should typically produce a voltage between 13.5 and 14.5 volts when the engine is running at a moderate RPM; a reading below this range signifies an undercharging condition.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6105M
• 6115M
• 6125M
• 6140M
• 6150M
• 6170M
• 6110
• 6210
• 6310
• 6120

1. 1

   Check the battery voltage with the engine off (should read approximately 12.6 volts). Fully charge the battery if discharged, as a weak battery can mimic alternator issues.

2. 2

   Inspect the alternator drive belt for proper tension, wear, and cracks. A loose or worn belt can slip and prevent the alternator from generating a charge.

3. 3

   Visually inspect the wiring harness, connectors, battery terminals, and ground connections for frayed wires, cracked insulation, looseness, or corrosion.

4. 4

   Check all fuses related to the charging circuit to ensure none are blown.

5. 5

   Perform a voltage output test with the engine running at approximately 1500 RPM. Measure DC voltage across the battery terminals (expected: 13.5 to 14.5 volts). If the voltage remains at the battery's static level or drops, the alternator is likely not charging. An overcharging condition (above 15.0V) suggests a failed voltage regulator.

6. 6

   Check the dashboard for a battery warning light that may flicker at low RPMs or stay on continuously. The absence of a battery light when the ignition is first turned on can also be a sign of a problem in the charging circuit.

1. 1

   Disconnect the Battery

   Disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Release Belt Tension

   Loosen the serpentine belt tensioner and remove the belt from the alternator pulley.

3. 3

   Remove Electrical Connections

   Disconnect the electrical connectors and the main power wire from the back of the alternator.

4. 4

   Remove Mounting Bolts

   Some models may require the removal of an idler pulley to access the alternator's mounting bolts. Once accessible, remove the bolts securing the alternator to its bracket.

5. 5

   Remove the Old Alternator

   Carefully remove the alternator from the engine.

6. 6

   Transfer Pulley (if necessary)

   Some replacement alternators may not come with a pulley. In such cases, the original pulley will need to be transferred to the new unit. This may require a special tool, especially for overriding pulleys that only spin in one direction.

7. 7

   Install the New Alternator

   Position the new alternator and secure it with the mounting bolts.

8. 8

   Reinstall Components

   Reinstall any components that were removed for access, such as the idler pulley.

9. 9

   Reconnect Electrical Connections

   Attach the electrical connectors and the main power wire to the new alternator.

10. 10

    Reinstall the Belt

    Route the serpentine belt correctly and release the tensioner to tighten it.

11. 11

    Reconnect the Battery

    Reconnect the negative battery cable.

12. 12

    Verify the Repair

    Start the engine and re-run the voltage output test to confirm that the new alternator is charging correctly, with a voltage reading between 13.5 and 14.5 volts.