Case IH 518985-03 - BCM – BCM: Work lamp #7 - short circuit to B+

The electrical circuit supplying power to Work Lamp #7 is receiving battery voltage (12V / B+) when it should not be. This is typically caused by a wiring harness shorting to a live power wire, a failed switch, or an internal fault within the control module bridging the power circuit.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect
• Case IH Steiger / Quadtrac AFS Connect

1. 1

   Identify Work Lamp #7: Consult the operator's manual or AFS Pro 1200 monitor to identify the physical location of Work Lamp #7 (cab roof, fender, or grille).

2. 2

   Harness Voltage Test: Disconnect the connector at Work Lamp #7. With the tractor key ON but the work light switch OFF, use a multimeter to measure the voltage at the harness connector. If it reads 12V, the short to B+ is actively present in the harness.

3. 3

   Visual Harness Inspection: Trace the wiring harness from Work Lamp #7 back to the BCM. Look for pinched wires, chafing against the tractor frame, or melted insulation where the work lamp wire might be touching a constant 12V wire.

4. 4

   BCM Pin Inspection: Disconnect the lighting harness connector at the BCM. Inspect the pins for water ingress, corrosion, or bent pins that could be bridging a 12V power pin to the Work Lamp #7 output pin.

5. 5

   Component Isolation: If the harness tests fine, the short may be internal to the work lamp assembly itself or the BCM.

1. 1

   Disconnect Power

   Turn off the tractor and engage the manual battery isolator switch (managed by the BCM) to disconnect all power before servicing the electrical system.

2. 2

   Repair the Harness

   If a short to B+ was found in the wiring harness during diagnostics, cut out the damaged section of wire. Splice in a new section of wire using weather-sealed heat-shrink butt connectors, ensuring it is routed away from pinch points.

3. 3

   Replace the Lamp

   If the harness and BCM are outputting correct voltages but the lamp assembly is internally shorted, unbolt the lamp housing, disconnect the pigtail, and install a replacement OEM work lamp.

4. 4

   Reconnect and Clear Codes

   Reconnect the battery isolator. Turn the ignition ON and use the AFS Pro 1200 monitor (or the Case IH Electronic Service Tool) to clear the inactive 518985-03 fault code.

5. 5

   Test Operation

   Turn on the work lights via the Integrated Control Panel (ICP) or armrest to verify Work Lamp #7 illuminates correctly without throwing a new code.