Case IH 520434-04 - BCM – BCM: Alternator feedback - out of range - low

The control module detects that the feedback voltage or PWM signal from the alternator is falling below the expected operational threshold. This typically indicates that the alternator is not charging properly, the internal voltage regulator has failed, or there is a short-to-ground/open circuit in the feedback wiring.

• MAGNUM AFS Connect
• Magnum 340
• Magnum 400 AFS Connect

1. 1

   Battery Voltage Test: Measure voltage at the battery with the engine off (should be around 12.6V) and with the engine running (should be between 13.5V and 14.5V). A reading below 13.5V while running confirms a charging system failure.

2. 2

   Wiring Harness Inspection: Inspect the feedback circuit wire running between the alternator's regulator plug and the BCM. Look for chafing, broken wires, or corrosion that could cause an 'out of range low' (short to ground or open circuit) reading.

3. 3

   Drive Belt Check: Ensure the serpentine/alternator drive belt is properly tensioned and not slipping or heavily worn.

4. 4

   Terminal Inspection: Check the B+ terminal on the alternator and the battery terminals for severe corrosion or loose connections.

1. 1

   Disconnect Power

   Disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Remove the Belt

   Use a tensioner tool to relieve pressure on the drive belt tensioner and slip the serpentine belt off the alternator pulley.

3. 3

   Disconnect Wiring

   Disconnect the B+ heavy gauge charge wire and unplug the electrical regulator/feedback connector from the back of the alternator.

4. 4

   Remove the Alternator

   Remove the alternator mounting bolts and carefully extract the heavy unit from the engine bay.

5. 5

   Install the New Alternator

   Position the new alternator, insert and torque the mounting bolts to OEM specifications.

6. 6

   Reconnect Components

   Reconnect the B+ charge wire and the regulator/feedback plug. Re-route and install the serpentine belt, ensuring it is seated correctly on all pulleys.

7. 7

   Test

   Reconnect the negative battery cable. Start the tractor and verify that the charging voltage is within the 13.5V–14.5V range and that fault code 520434-04 has cleared from the BCM.