Case IH 520570-03 - BCM – BCM: Rear wiper motor - short circuit to B+

The control module has detected that the electrical circuit supplying or controlling the rear windshield wiper motor is shorted directly to battery positive voltage (B+). This condition prevents the module from properly grounding or regulating the circuit, usually resulting in a wiper motor that runs continuously, fails to park, or is completely inoperative to protect the circuit.

• MAGNUM AFS Connect
• Magnum 180 AFS Connect
• Magnum 200 AFS Connect
• Magnum 220 AFS Connect
• Magnum 240 AFS Connect
• Magnum 250 AFS Connect
• Magnum 280 AFS Connect
• Magnum 310 AFS Connect
• Magnum 340 AFS Connect
• Magnum 380 AFS Connect
• Magnum 400 AFS Connect

1. 1

   Check Fuses: Verify that the BCM and rear wiper circuit fuses are intact. A short to B+ can sometimes backfeed and blow related circuit protection.

2. 2

   Inspect the Wiring Harness: Trace the wiring from the BCM to the rear wiper motor connector. Look for chafed wires, pinched harnesses (especially near the cab window hinge points), or melted insulation where the wiper control wire might be touching a constant 12V power source.

3. 3

   Test the Wiper Switch: Perform a diagnostic test on the rear wiper switch (Test point G-6/D) to ensure the switch itself is not internally shorted and sending a constant high signal to the BCM.

4. 4

   Test the Motor (Test point G-8): Disconnect the rear wiper motor. If the fault code changes from 'Short to B+' to an 'Open Circuit' code, the short is likely internal to the wiper motor itself. If the code remains 'Short to B+', the short is in the wiring harness between the BCM and the motor connector.

1. 1

   Disconnect Power

   Turn off the battery disconnect switch to prevent any electrical spikes to the BCM during repair.

2. 2

   Remove the Wiper Arm

   Lift the plastic cover at the base of the rear wiper arm. Remove the retaining nut (typically 13mm or 15mm) securing the arm to the motor spindle. Carefully pull the wiper arm off the splined shaft.

3. 3

   Access the Motor

   Inside the cab, remove the plastic BCM/wiper motor cover on the rear window frame to expose the motor assembly.

4. 4

   Disconnect Electricals

   Unplug the wiring harness connector from the rear wiper motor.

5. 5

   Dismount the Motor

   Remove the mounting bolts holding the motor bracket to the rear glass/cab frame. Carefully extract the motor, ensuring you do not lose the rubber isolation grommets.

6. 6

   Install the New Motor

   Position the new motor and tighten the mounting bolts. Crucial step: Ensure the rear wiper motor spindle seal is properly seated against the glass to prevent water ingress.

7. 7

   Reassembly

   Reconnect the electrical harness, reinstall the interior plastic cover, and reattach the exterior wiper arm (tighten the spindle retaining nut to OEM torque specs).

8. 8

   Clear Codes

   Restore battery power, clear the inactive 520570-03 code from the BCM via the AFS Pro display, and test the wiper for proper operation and parking.