Case IH 518689-02 - ACM – ACM: Rear hitch max height switch circuit fault

An electrical circuit error (such as an open circuit, short to ground, or short to power) in the potentiometer/encoder dial used by the operator to set the maximum lifting height of the rear 3-point hitch. Because the module cannot read a valid signal, the rear hitch may default to a safe mode or fail to raise to the desired height.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect Series (Magnum 250, 280, 310, 340, 380, 400)
• Case IH Steiger & Quadtrac AFS Connect Series
• Case IH Optum AFS Connect Series

1. 1

   Inspect the physical condition of the rear hitch max height encoder dial on the Multicontroller armrest for physical damage or sticking.

2. 2

   Carefully remove the armrest control panel cover and inspect the wiring harness and the specific connector going to the max height switch for loose wires, bent pins, or corrosion.

3. 3

   Using a multimeter, check the wiring between the switch and the main ACM board for continuity. Test for an open circuit, short to ground, or short to voltage.

4. 4

   Verify that the ACM is supplying the correct reference voltage (usually 5V) and ground to the switch.

5. 5

   Test the potentiometer's resistance while turning the dial to ensure the resistance changes smoothly without dropouts or dead spots.

1. 1

   Disconnect Power

   Turn off the tractor ignition and disconnect the negative battery cable to prevent electrical damage.

2. 2

   Access the ACM

   Carefully remove the retaining screws and pry up the trim panels on the Multicontroller armrest to expose the internal switch clusters and wiring.

3. 3

   Locate the Switch

   Identify the rear hitch max height switch/potentiometer assembly on the underside of the panel.

4. 4

   Disconnect

   Unplug the electrical harness connector from the faulty switch.

5. 5

   Remove

   Remove the retaining clips or Torx screws holding the switch in the armrest housing and pull the switch out.

6. 6

   Install

   Insert the replacement switch/encoder, secure it with the fasteners, and plug in the electrical connector.

7. 7

   Reassemble

   Carefully route the wiring harness to ensure it won't be pinched, then snap the armrest trim panels back into place and reinstall the screws.

8. 8

   Clear Codes & Calibrate

   Reconnect the battery. Turn on the ignition and use the AFS Pro 1200 display (or a dealer diagnostic tool) to clear the 518689-02 fault code. Test the rear hitch to ensure it respects the newly set maximum height limit.