Case IH 518558-02 - ACM – ACM: EHR settings adjustment knob switch circuit fault

This indicates an electrical circuit failure—such as an open circuit, short to ground, or erratic voltage—originating from the Electronic Hitch Control (EHR) settings adjustment encoder/knob switch.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect series
• Case IH Puma series
• Case IH Steiger AFS Connect series

1. 1

   Check fault status using the AFS Pro 1200 monitor or Case IH Electronic Service Tool (EST) to determine if the code is Active or Stored.

2. 2

   Monitor switch inputs in the diagnostics menu (Settings > Tractor > Diagnostic Trouble Codes) or EST to observe if the controller registers any input when the EHR knob is turned.

3. 3

   Inspect the wiring harness and connectors between the EHR settings adjustment knob and the Armrest Control Module (ACM) for pinched wires, corrosion, or loose pins.

4. 4

   Test the switch's resistance and voltage to check for shorts, noting that static discharge can short filter capacitors on the inputs to the ICs on the armrest board.

1. 1

   Disconnect Power

   Disconnect the tractor's battery power. The Armrest Control Module is highly sensitive to static discharge and voltage spikes.

2. 2

   Access the ACM

   Open the armrest controller housing by removing the screws holding the upper and lower shells together.

3. 3

   Isolate the Switch

   Locate the EHR settings adjustment knob/encoder on the armrest board and disconnect its specific wire harness connector.

4. 4

   Test/Replace

   Test the switch with a multimeter. If the switch/encoder is faulty, replace the knob/encoder assembly. If the switch tests fine but the fault persists, the ACM board itself may have a failed component (such as a blown EMI suppression filter or shorted capacitor) requiring board repair or replacement.

5. 5

   Reassembly

   Install the new switch/encoder, reconnect the harness, and reassemble the upper and lower armrest shells.

6. 6

   Recalibrate

   Reconnect the battery, turn the key on, and use the EST or AFS Pro monitor to clear the fault code. You will likely need to recalibrate the EHR remote valves and settings via the monitor before operating the machine.