John Deere 002350.03 – BLC, RLC, VLC, CLC: Voltage Detected at Headlight Low Beam Pin When Headlights Are Off

The lighting control module has detected voltage on the low-beam headlight circuit even when the headlights are commanded to be off. This abnormal condition indicates a voltage backfeed or a short to power within the wiring loom, causing the circuit to remain energized.

• 6000 Series
• 7220
• 7320
• 7420
• 7520
• 9230
• 9330
• 9430
• 9530
• 9630
• Lawn Tractors
• Gators
• ZTrak Mowers

1. 1

   Cycle the ignition and light switch to verify if the low-beam headlights stay on or glow dimly when they should be off.

2. 2

   Check the battery voltage (must be at least 12.6V with the engine off) and ensure all battery terminals, starter connections, and main chassis/engine ground straps are clean, tight, and free of corrosion.

3. 3

   Inspect fuses related to the headlights and the relevant lighting controller for blown fuses, which would indicate a short circuit.

4. 4

   Inspect the headlight relays to ensure they are not stuck in the closed position.

5. 5

   Visually inspect the wiring harness leading to the low-beam headlights and from the lighting switch for chafing, melting, rodent damage, pinched wires, or connector corrosion.

1. 1

   Isolate the circuit

   Disconnect the electrical connector at both low-beam headlight bulbs. Turn the ignition on with the headlight switch off.

2. 2

   Test for stray voltage

   Using a multimeter set to DC Volts, probe the low-beam power pin in one of the headlight connectors. Place the black probe on a known good chassis ground. A reading of approximately 12V confirms the FMI 03 short-to-power condition.

3. 3

   Diagnose bad ground (Backfeed)

   Check the ground wires and connection points for the headlights. A poor ground can cause power from another circuit (like high beams or park lights) to feed back through the low-beam filament to find a ground path.

4. 4

   Check for shorted wiring

   Trace the low-beam wire from the controller to the headlight and check for continuity with other wires in the harness that have power when the key is on. Use a machine-specific wiring diagram for this step.

5. 5

   Test headlight switch

   Disconnect the headlight switch. If the voltage at the headlight connector disappears, the internal contacts of the main light switch or dimmer switch are likely faulty and crossing power.

6. 6

   Test headlight relay

   If the circuit uses a relay, swap the headlight relay with a known good relay of the same part number to test if the internal contacts are stuck closed.

7. 7

   Inspect control module

   If all wiring, switches, relays, and grounds check out, the fault may lie within the lighting control module itself (internally shorted output driver). This should be the last item suspected.

8. 8

   Repair and verify

   Repair or replace the identified faulty component. Reconnect all components, clear the fault codes by cycling the ignition or using the diagnostic display, and verify the headlights operate correctly.