Case IH 520561-03 - BCM – BCM: Short circuit to B+ in the rear windshield washer motor circuit

The control module has detected battery voltage (B+ / 12V) on a circuit that should not currently have it (such as a ground line or a switched control line that is supposed to be off). This condition is typically caused by a wiring harness failure (e.g., a wire chafing against a live 12V power wire), a failed internal switch, or an internal short within the washer motor itself.

• MAGNUM AFS Connect
• Magnum
• Puma
• Maxxum
• Optum
• Steiger
• Farmall

1. 1

   Check the Dashboard: Look for active amber warning lights and read the freeze-frame data on the AFS Pro display to see the exact conditions when the fault occurred.

2. 2

   Visual Wiring Inspection: Inspect the wiring harness leading from the BCM to the rear washer motor. Look for pinched, chafed, or melted wires, especially where the harness routes through cab pillars, near hinges, or along the roof.

3. 3

   Voltage Test: Disconnect the rear washer motor connector. Using a multimeter, check for unwanted battery voltage on the control/ground pins while the washer switch is in the 'OFF' position.

4. 4

   Switch Test: Test the rear washer switch/stalk on the steering column or side console to ensure it is not internally shorted and sending constant voltage.

5. 5

   Motor Resistance Test: Measure the internal resistance of the washer motor to determine if the windings have shorted internally.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent further electrical damage or accidental shorting during repair.

2. 2

   Access the Motor

   Locate the rear windshield washer motor. Depending on the model, it is typically mounted directly on the washer fluid reservoir or routed in the rear cab roof.

3. 3

   Repair Wiring (If Applicable)

   If the diagnostic checks revealed a damaged wiring harness, repair the chafed or broken wires using proper automotive-grade splices and heat shrink. Ensure the harness is re-routed away from sharp edges.

4. 4

   Replace the Motor (If Applicable)

   If the motor is internally shorted, disconnect the fluid hoses and the electrical connector. Unbolt or unclip the old motor and install the replacement pump.

5. 5

   Reassemble and Reconnect

   Reconnect the fluid lines, electrical connector, and the battery.

6. 6

   Clear Codes

   Turn the ignition on and use a CNH diagnostic tool (or cycle the key, depending on the model) to clear the stored fault codes.

7. 7

   System Test

   Test the rear washer system to confirm the short circuit is resolved and fluid sprays correctly onto the rear glass.