Full fielding an alternator is a diagnostic procedure used to test the functionality of the alternator and its voltage regulator. This method momentarily bypasses the voltage regulator, allowing the alternator to operate at maximum output. This guide provides a comprehensive overview of how to perform this test safely and effectively.

Understanding Full Fielding

Full fielding is primarily used when an alternator is suspected of malfunctioning, particularly when it fails to charge the battery properly. By directly energizing the rotor, you can determine if the issue lies with the alternator itself or the voltage regulator.

Why Full Field an Alternator?

  • Diagnose Charging Issues: If the alternator is not charging, full fielding helps identify whether the problem is with the alternator or the voltage regulator.
  • Test Performance: It allows technicians to check if the alternator can produce maximum voltage output when unregulated.

Steps to Full Field an Alternator

1. Safety Precautions: Ensure that you are wearing safety gloves and goggles. Disconnect the battery before starting any work on the electrical system.

2. Locate the Alternator: Identify your vehicle's alternator and locate its wiring harness.

3. Identify Field Terminals: Find the field terminals on the back of the alternator. These are usually labeled F or DF (field) and D- (ground).

4. Prepare for Testing:

- Disconnect the two-pin connector from the alternator.

- Use insulated wires to prevent accidental shorts.

5. Connect for Full Fielding:

- Connect one field terminal (typically DF) to a known good ground.

- Connect the other terminal (D-) to a fused jumper wire (10 amp fuse).

- Attach the other end of this jumper wire to a positive voltage source, such as the battery.

6. Start the Engine: With everything connected, start your vehicle and bring it to around 1500 RPM.

7. Monitor Voltage Output:

- Use a multimeter to check the voltage at the B+ terminal of the alternator.

- If functioning correctly, you should see a voltage rise above battery voltage, ideally between 13.5V and 16V.

8. Evaluate Results:

- If voltage rises significantly, it indicates that the alternator is functional, and the issue may be with the voltage regulator.

- If there is no increase in voltage, it suggests that there may be a fault within the alternator itself.

9. Disconnect Safely: After testing, carefully disconnect all wires in reverse order of connection, ensuring no short circuits occur.

Important Considerations

  • Voltage Regulation: Remember that full fielding bypasses normal regulation; do not keep it connected for long periods as it can damage electrical components.
  • Alternator Type: Be aware that some modern vehicles have integrated regulators that may complicate this process.

FAQs About Full Fielding an Alternator

    • What tools do I need?
      A multimeter, insulated jumper wires, and safety equipment.
    • Can I perform this test on any vehicle?
      Not all vehicles are suitable; consult your vehicle's service manual.
    • What if my alternator still doesn't charge after full fielding?
      This could indicate internal damage to the alternator itself.