Case IH 518685-13 - ACM – ACM (Armrest Control Module): Hitch settings selector knob disconnected

The fault indicates an open circuit, loss of signal, or physical disconnection between the hitch settings selector knob (a potentiometer or rotary switch) and the Armrest Control Module. The system cannot detect the position of the knob, which is used by the operator to adjust rear hitch parameters such as draft control, position control, height limit, drop rate, or sensitivity.

• MAGNUM AFS Connect
• Magnum Series (e.g., MX Magnum, Series 4 235–340)
• Steiger Series (e.g., STX 350–600)
• Puma Series
• Maxxum Series (e.g., MX Maxxum)

1. 1

   Remove the armrest console cover and inspect the wiring harness leading to the hitch selector knob. Look for unplugged connectors, pinched wires, or backed-out pins.

2. 2

   The ACM supplies a 5-volt reference to armrest potentiometers. Check if the 5V reference is present at the switch connector. (Related codes like 1014 or 1015 indicate 5V reference issues across the whole module).

3. 3

   Use a multimeter to test the resistance sweep of the selector knob potentiometer. If the resistance reads out of limits (OL) or has dead spots as you turn it, the switch has failed internally.

4. 4

   Connect a diagnostic tool (e.g., Jaltest, EASY tool, or the tractor's AFS Pro display diagnostics) to monitor the live data for the hitch selector knob. If the value reads 0V or 5V constantly while turning the knob, the circuit is open or shorted.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent short circuits while working inside the armrest console.

2. 2

   Disassemble Armrest

   Remove the retaining screws securing the top cover or side panel of the armrest control console to access the internal switch matrix.

3. 3

   Remove the Faulty Switch

   Locate the hitch settings selector knob. Disconnect its electrical pigtail/connector.

4. 4

   Extract the Component

   Pull off the plastic operator knob from the top of the console. Remove the retaining nut or mounting screws holding the potentiometer/switch body to the armrest panel.

5. 5

   Install the New Part

   Insert the new switch into the panel, secure it with the retaining nut, and press the plastic knob back onto the splined shaft.

6. 6

   Reconnect

   Plug the electrical connector back into the switch harness.

7. 7

   Reassemble and Calibrate

   Reinstall the armrest covers and reconnect the battery. Turn the key on and use the tractor's display or a diagnostic tool to clear the inactive fault codes. Perform a hitch controller calibration if required by the service manual to teach the ACM the new potentiometer's minimum and maximum voltage values.