Case IH 520445-05 - BCM – BCM: Left Roof-Mounted Low Beam Headlamp Open Circuit

Fault code 520445-05 indicates an "open circuit" condition on the left roof-mounted low beam headlamp. An open circuit means there is a break in the electrical path preventing current from flowing. This is most commonly caused by a blown bulb filament, a disconnected or damaged wiring connector, a broken wire in the harness, or a failed ground connection.

• MAGNUM AFS Connect
• Magnum 400 AFS Connect

1. 1

   Remove the left roof-mounted headlamp bulb from its socket and perform a visual inspection of the filament. A broken filament indicates an internal open circuit.

2. 2

   Perform a voltage test at the headlight socket using a multimeter set to DC volts. Turn the headlight switch to the low beam position.

3. 3

   If the socket reads 12–14 V, the circuit is supplying power correctly, meaning the bulb itself is the source of the open circuit or there is poor contact/corrosion inside the socket.

4. 4

   If the socket reads 0 V, no power is reaching the bulb. You must then check the wiring harness, relays, and the BCM for breaks or disconnected plugs.

5. 5

   Inspect the headlight connector pigtail and terminals for physical damage, pushed-out pins, or corrosion.

1. 1

   Prepare machine

   Turn off the tractor and ensure the headlight switch is in the OFF position.

2. 2

   Access headlamp assembly

   Access the left roof-mounted headlamp assembly on the cab roof.

3. 3

   Disconnect pigtail connector

   Remove the headlight socket cover and unplug the light socket pigtail connector.

4. 4

   Replace bulb (if blown)

   If the diagnostic tests revealed a blown bulb (open internal circuit), replace the bulb with a new one, ensuring it is seated correctly in the housing.

5. 5

   Repair wiring or connector (if no voltage)

   If the diagnostic tests revealed 0 V at the socket or a damaged connector, replace the damaged connector pigtail or repair the broken wire in the harness leading back to the BCM.

6. 6

   Reconnect pigtail plug

   Reconnect the headlamp pigtail plug and reinstall the socket cover.

7. 7

   Test headlights

   Turn the tractor's ignition on and test the low beam headlights to ensure the open circuit fault code has cleared and the light functions properly.