John Deere CAB523639 – CAB: Right Rear Red Light Open Circuit in Lighting System - Hazard

The Cab Control Unit (CAB) has detected an open circuit in the electrical path for the right rear red hazard light. This indicates a break in wire continuity, a loose connection, or a failed component preventing electrical current from flowing. Consequently, the right rear hazard light fails to illuminate when the hazard or turn signal system is activated, which impacts the visibility of the hazard warning. A low current draw below 0.5 amps can also trigger this fault.

• 4200
• 4300
• 4400
• 5200
• 5300
• 5400
• 5E
• 5D

1. 1

   Visually inspect the right rear red light assembly for any visible damage, cracks, or moisture ingress, and check the wiring harness leading to the light for any signs of chafing, pinching, or fraying.

2. 2

   Remove the bulb from the right rear light assembly, inspect the filament for breaks, and test with a known good bulb.

3. 3

   Check the fuse panel for any blown fuses related to the lighting or hazard circuits, specifically checking fuse F15 for CAB switched power.

4. 4

   Disconnect the wiring harness connector at the right rear light to inspect terminals for corrosion, dirt, or looseness, clean them, and trace the harness back towards the cab.

5. 5

   With hazard lights activated, use a multimeter to check for voltage at the right rear light connector to determine if the open circuit is upstream in the wiring or at the control module.

6. 6

   Verify that the ground wire for the light assembly has a clean and secure connection to the tractor's chassis.

1. 1

   Locate control module

   If basic electrical checks do not resolve the issue, locate the turn signal and hazard control module. It is typically a small box with relays located under the dashboard. On 4000 series tractors, remove the dash and side panels for access.

2. 2

   Disconnect module

   Carefully disconnect the electrical connector from the module. Wiggle it gently to avoid breaking the plastic, which can become brittle over time.

3. 3

   Remove old module

   Unscrew the retaining nut on the back of the dash to release and remove the old control module.

4. 4

   Install new module

   Position the new turn signal/hazard control module and secure it with the retaining nut.

5. 5

   Reconnect and test

   Reconnect the electrical connector. Turn on the tractor's electrical system and test the hazard lights and turn signals to confirm the repair.

6. 6

   Reassemble panels

   Once function is confirmed, reassemble the dash and any other panels that were removed.