Case IH 520441-14 - BCM – BCM: Mirror heat switch - invalid input voltage

The control module detects that the electrical signal coming from the heated mirror switch falls outside the expected voltage parameters. This typically points to a damaged switch, a short circuit, an open circuit, or a poor ground connection in the switch wiring.

• MAGNUM AFS Connect
• Magnum AFS Connect Series
• Magnum 220
• Magnum 250
• Magnum 340
• Puma
• Maxxum
• Steiger
• Quadtrac
• Farmlift 526
• 521F
• 621F
• 721F
• FR920 Forage Harvesters
• LM6.28/TH5.26 Telehandlers

1. 1

   Verify system voltage to ensure the battery and alternator are supplying proper voltage, as low voltage can trigger invalid input faults.

2. 2

   Inspect the mirror heat switch connector (X127) on the cab roof harness for corrosion, moisture, or pushed-out terminals.

3. 3

   Perform a wiring continuity test between the switch connector and the BCM, checking for continuity, short-to-ground, or short-to-power.

4. 4

   Test the switch for internal resistance to see if it outputs an erratic signal when toggled, indicating internal failure.

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery cable to prevent electrical shorts while working on the BCM circuits.

2. 2

   Access the Switch

   Carefully pry off the necessary cab trim panels or the switch bezel on the A-pillar/roof console to access the rear of the mirror heat switch.

3. 3

   Disconnect

   Unplug the electrical harness (Connector X127) from the back of the switch.

4. 4

   Remove the Switch

   Depress the retention tabs on the sides of the faulty switch and push it out of the mounting panel.

5. 5

   Install the New Part

   Snap the new OEM mirror heat switch into the panel until the retention tabs click into place.

6. 6

   Reconnect

   Plug the electrical connector back into the switch, ensuring the locking tab engages.

7. 7

   Reassemble and Power Up

   Reinstall the cab trim panels and reconnect the battery.

8. 8

   Clear Codes

   Turn the ignition on. Use a diagnostic tool (such as the Case IH EST or Jaltest) to clear the stored 520441-14 fault code from the BCM. Test the mirror heater to ensure the code does not return and the mirrors warm up.