Case IH 518685-06 - ACM – ACM: Hitch settings selector knob voltage low

The signal voltage from the hitch settings selector knob (which operates via a potentiometer) has dropped below the minimum acceptable threshold (typically below 0.5V on a 5V reference circuit), indicating a short to ground in the wiring, a disconnected plug, or an internally failed potentiometer.

• MAGNUM AFS Connect
• Magnum Series (180, 200, 220, 240, 235-340)
• Steiger Series
• Puma Series
• Optum and Vestrum CVXDrive Series

1. 1

   Check system voltage to ensure the tractor's battery and charging system are functioning properly (12-14 volts), as low voltage can cause erratic module behavior.

2. 2

   Remove the armrest cover and visually inspect the wiring harness leading to the hitch settings selector knob for pinched wires, chafing, or exposed copper shorting to the chassis or ground.

3. 3

   Disconnect the plug at the hitch settings potentiometer and check for bent pins, corrosion, or moisture.

4. 4

   Turn the key to the ON position and use a multimeter to verify that the potentiometer is receiving a steady 5V reference signal from the ACM.

5. 5

   Check the ground circuit for continuity.

6. 6

   Test the signal wire for a short to ground. If the 5V, ground, and signal wiring are intact, the potentiometer has failed internally.

1. 1

   Power Down

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

2. 2

   Access the Armrest

   Remove the retaining screws for the Multicontroller armrest top cover/bezel to expose the internal switches and the ACM.

3. 3

   Remove the Faulty Component

   Locate the hitch settings selector knob. Disconnect its electrical harness connector. Remove the retaining nut or mounting screws holding the potentiometer to the armrest housing and pull the switch out.

4. 4

   Install the New Part

   Insert the replacement potentiometer into the armrest housing and secure it with the retaining hardware. Reattach the selector knob to the shaft.

5. 5

   Reconnect

   Plug the electrical connector back into the new potentiometer.

6. 6

   Reassemble

   Reinstall the armrest cover and secure all screws. Reconnect the tractor's battery.

7. 7

   Calibration

   Power on the tractor. Navigate to the tractor's display (e.g., AFS Pro 700/1200) or instrument cluster menu. Enter the 'HITCH CAL' (Hitch Calibration) menu to calibrate the new potentiometer's minimum and maximum travel values so the ACM can learn the new sensor's sweep.

8. 8

   Clear Codes

   Clear the inactive 518685-06 fault code from the ACM memory and test the hitch operation.