Case IH 4026-00 - BCM – BCM: Right mirror heater - circuit overload - too many loads or faulty load

The control module has detected that the electrical current draw on the right mirror heater circuit has exceeded the maximum allowable threshold. This condition is typically caused by a short to ground in the vehicle's wiring harness or an internally shorted/faulty mirror heater element that is pulling too much amperage.

• MAGNUM AFS Connect
• Magnum 235–340 (Series 4)
• Optum AFS Series
• Steiger AFS Series
• Farmall Series

1. 1

   Use a diagnostic scan tool to verify that the 4026-00 code is currently active in the BCM.

2. 2

   Inspect the wiring harness routed to the right outside mirror. Look for chafed, pinched, or exposed wires that could be causing a short to the vehicle chassis ground.

3. 3

   Disconnect the electrical connector at the right mirror heater element. If the fault changes from a 'circuit overload' to an 'open circuit' code, the wiring is likely intact, and the fault is isolated to the heater element itself.

4. 4

   Use a multimeter to test the resistance of the right mirror heater element. A reading of zero or near-zero ohms indicates an internal short circuit.

1. 1

   Power down the tractor

   Power down the tractor and turn off the battery disconnect switch to prevent further electrical damage.

2. 2

   Repair or replace damaged wiring harness

   If the wiring harness is damaged (shorted to ground), repair the affected wires using appropriate automotive-grade wire and heat-shrink tubing, or replace that section of the harness.

3. 3

   Remove faulty mirror glass

   If the mirror heater element is faulty, carefully pry or unclip the right mirror glass assembly from the exterior mirror housing.

4. 4

   Disconnect electrical terminals

   Disconnect the electrical spade terminals from the back of the faulty heated mirror glass.

5. 5

   Connect replacement mirror glass

   Connect the wiring terminals to the replacement heated mirror glass.

6. 6

   Install new mirror glass

   Carefully snap the new mirror glass back into the mirror housing motor/bracket.

7. 7

   Restore power and test

   Restore battery power, turn the ignition on, and activate the mirror heater switch.

8. 8

   Clear fault code

   Use a diagnostic tool to clear the 4026-00 fault code from the BCM and verify that the code does not return when the circuit is under load.