John Deere 3976.06 – RLC (Roof Lighting Control Unit): Cab Dome Light High Amp Draw

The control software has detected that the high-side circuit supplying power to the front and rear dome lights (designated as components E15 and E16) is drawing excessive current. This is typically caused by the circuit's power wire (specifically the L107 BROWN wire) being shorted to ground.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 859M
• 903M
• 953M
• 959M
• 9470RT
• 9520RT
• 9570RT

1. 1

   Remove the dome light bulbs (E15 and E16) and inspect them for internal shorts or melted filaments that could cause a high amperage draw.

2. 2

   Using a multimeter, test the L107 BROWN wire (the high-side circuit wire for the dome lights) for continuity to ground.

3. 3

   Trace the wiring from the dome light fixtures back to the RLC module, looking for pinched, chafed, or exposed wires, particularly where the harness routes through the cab roof frame.

4. 4

   Inspect the connectors at the RLC module and the dome light fixtures for corrosion, moisture, or melted pins.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical shock or further module damage.

2. 2

   Access the Roof Harness

   Remove the interior cab roof liner or access panels to expose the RLC module and the dome light wiring harness.

3. 3

   Isolate the Short

   Disconnect the dome light fixtures (E15 and E16) from the harness. Reconnect the battery and test the circuit. If the high amp draw/short is gone, the fault is inside the light fixture or bulb. If the short persists, the fault is in the wiring harness.

4. 4

   Repair Wiring

   If the L107 BROWN wire is chafed and shorting against the metal cab frame, cut out the damaged section, splice in a new piece of wire using weather-resistant heat-shrink butt connectors, and wrap the harness in protective loom.

5. 5

   Replace Components

   If the light fixture or bulb is internally shorted, replace it with a new OEM component.

6. 6

   Reassemble and Clear Codes

   Reconnect all fixtures, reinstall the roof liner, and reconnect the battery. Turn the key on and use a diagnostic tool (or the machine's onboard display) to clear the RLC 003976.06 code. Test the dome lights to ensure proper operation.