Case IH 518504-05 - BCM – BCM: Cab recirculation blower motor control signal - open circuit

The Body Control Module (BCM) monitors the electrical circuits that control the cab's HVAC system. An "open circuit" (indicated by the -05 failure mode identifier) means there is a physical break in the electrical path of the control signal wire going to the cab recirculation blower motor. The BCM is attempting to send a voltage signal to command the blower motor to spin, but it detects zero current flow. This condition disables the recirculation fan, which can lead to poor climate control performance inside the cab.

• MAGNUM AFS Connect
• Magnum 340 AFS Connect
• Magnum 380 AFS Connect
• Magnum 400 AFS Connect
• Steiger AFS Connect

1. 1

   Check the cab fuse panel for any blown fuses related to the HVAC system or cab blowers (a blown fuse usually indicates a short, but should be verified first).

2. 2

   Access the recirculation blower motor, disconnect the electrical harness, and visually inspect the connector pins for corrosion, moisture, or pins that have pushed out of the plastic housing.

3. 3

   With the key ON and the HVAC system commanded to operate the recirculation fan, use a multimeter to check for control voltage at the blower motor connector.

4. 4

   Verify that the ground wire at the blower motor connector has good continuity (low resistance) to the chassis ground.

5. 5

   If no voltage is present on the control wire, test the continuity of the harness from the BCM output pin to the blower motor connector to locate the break in the wire.

6. 6

   If power, ground, and the control signal are all present at the connector but the motor does not run, the internal circuitry of the blower motor is open and the motor assembly must be replaced.

1. 1

   Park the tractor on a level surface, turn off the engine, and disconnect the battery ground cable to prevent electrical shorts during repair.

2. 2

   Access the HVAC blower assembly. On Magnum tractors, the HVAC unit is located in the cab roof. You will need to remove the outer cab roof top cover or drop the interior headliner panel (depending on the specific cab configuration) to access the blower motors.

3. 3

   Locate the recirculation blower motor assembly within the HVAC plenum.

4. 4

   Disconnect the electrical harness connector from the faulty blower motor.

5. 5

   Remove the retaining screws or bolts securing the blower motor housing to the HVAC unit.

6. 6

   Carefully extract the faulty blower motor assembly.

7. 7

   Insert the replacement blower motor assembly into the housing and secure it with the retaining hardware.

8. 8

   Reconnect the electrical harness, ensuring the connector clicks into place securely.

9. 9

   Reinstall the cab roof cover or interior headliner components.

10. 10

    Reconnect the battery, turn the key ON, and test the HVAC system in both automatic and manual modes to verify the recirculation blower operates and the 518504-05 fault code is cleared.