Case IH 520564-03 - BCM – BCM: Short circuit to B+ on the circuit controlling the Cab Right Wiper Motor

The control module is detecting voltage on the right wiper motor's control circuit that is higher than expected or present when the circuit should be off. This usually happens when the control wire has chafed and is making direct contact with a live 12V power wire, or if there is an internal short within the wiper motor or the wiper switch itself. Symptoms typically include the right wiper running continuously (unable to be turned off), blowing fuses, or failing to operate entirely due to the module disabling the circuit to protect itself.

• MAGNUM AFS Connect
• Magnum 215
• Magnum 250
• Magnum 340
• Steiger series
• Puma
• Optum
• AFX8010
• Axial-Flow models

1. 1

   Inspect the wiring harness running from the BCM to the right side of the cab roof/headliner (or lower front right window) for pinched wires, melted insulation, or areas where the harness rubs against the cab frame.

2. 2

   Disconnect the electrical connector at the right wiper motor. With the key ON and the wiper switch OFF, use a multimeter to check for voltage at the control pin. If 12V is present, the short to B+ is in the wiring harness or the switch.

3. 3

   Disconnect the wiper switch/stalk. If the voltage on the motor control wire drops to 0V, the switch has an internal short and must be replaced.

4. 4

   If the wiring and switch test fine, the internal circuitry of the wiper motor itself has likely shorted to its constant power supply.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent electrical spikes or further damage to the BCM.

2. 2

   Access the Motor

   Remove the interior cab trim panels or headliner on the right side to access the right wiper motor assembly.

3. 3

   Repair Wiring

   If the diagnostic checks revealed a shorted wire in the harness, cut out the damaged section. Splice in a new section of wire using weather-resistant crimp connectors and heat-shrink tubing.

4. 4

   Replace the Motor

   Remove the exterior wiper arm from the splined/tapered shaft. Disconnect the electrical harness from the motor. Unbolt the motor mounting bracket from the cab frame and remove the old motor. Install the new motor, secure the bolts, and reconnect the electrical harness.

5. 5

   Reassembly and Testing

   Reconnect the battery. Turn the key ON and test the wiper switch through all speeds and the park position. Ensure the fault code clears from the BCM display. Finally, reinstall the wiper arm and cab interior trim.