Case IH 2642-03 - BCM – BCM: Left mirror heater - short circuit to B+

The system is detecting battery voltage (B+) on the left mirror heater control circuit when it should not be present (e.g., when the heater is commanded off), or the circuit's current draw indicates a direct short to a power source.

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

1. 1

   Visually inspect the wiring harness routing from the left mirror assembly, down the cab A-pillar, and into the cab where it meets the BCM. Look for pinched wires, chafing, or melted insulation.

2. 2

   Disconnect the electrical connector at the left mirror glass and clear the codes. If the 2642-03 code changes to an open circuit code (2642-05), the short is internal to the mirror assembly. If it remains, the short is in the harness or BCM.

3. 3

   With the mirror heater switched OFF via the AFS Pro 1200 monitor, probe the heater supply wire at the mirror connector. A reading of ~12V indicates a short to power in the harness.

4. 4

   Inspect the BCM connectors for water ingress, corrosion, or bent pins that could be bridging a power terminal to the mirror heater output terminal.

1. 1

   Disconnect Power

   Turn off the tractor ignition and disconnect the negative battery cable to prevent electrical spikes during repair.

2. 2

   Access the Mirror Wiring

   Remove the back cover of the left mirror housing to access the heater element electrical connections.

3. 3

   Repair Wiring (If Applicable)

   If the diagnostic checks isolated the short to the harness (e.g., wires rubbed through in the mirror pivot arm), cut out the damaged section of the wire. Splice in a new section of wire using weather-resistant heat-shrink butt connectors.

4. 4

   Replace Mirror Glass (If Applicable)

   If the short is internal to the mirror's heating grid, carefully pry the old mirror glass off its motorized backing plate. Disconnect the two spade terminals for the heater. Connect the terminals to the new heated mirror glass and snap it firmly into the motorized actuator ring.

5. 5

   Reassemble and Test

   Reconnect the battery. Turn the key ON and use the AFS Pro 1200 display to clear the BCM fault codes. Turn on the mirror heater and verify that the glass warms up and the 2642-03 code does not return.