Case IH 3950-05 - BCM – BCM: Tractor horn - open circuit

The electrical circuit responsible for operating the tractor's horn has a break in continuity, a disconnected plug, or an internal failure within the horn itself preventing current flow.

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

1. 1

   Inspect the horn circuit fuses in the power distribution box (Fuse #16 5 AMP or Fuse #17 Jumper to Horn)

2. 2

   Locate the horn relay in the engine fuse box/power distribution box and test it for proper operation

3. 3

   Perform a visual inspection of the wiring harness leading to the horn assembly for disconnected plugs, chafed wires, or broken connections

4. 4

   Test the steering column switch to ensure the horn button is successfully closing the circuit when pressed

1. 1

   Verify the Code

   Confirm that fault code 3950-05 (BCM) is active.

2. 2

   Inspect Power & Ground

   Using a digital multimeter (DMM), check for voltage at the horn connector when the horn button is pressed. Check the ground circuit for an open.

3. 3

   Fuse/Relay Replacement

   If the fuse is blown or the relay fails testing, replace the affected component in the fuse box.

4. 4

   Component Testing

   If power and ground are reaching the horn connector but the horn does not sound, the horn assembly has an internal open circuit and must be replaced.

5. 5

   Switch Testing

   If no power reaches the horn and the wiring is intact, test the steering column switch. Replace the switch assembly if the horn button contact is broken.

6. 6

   Clear Codes

   Reconnect all components, clear the BCM fault codes, and test the horn to verify the repair.