Case IH 518687-02 - ACM – ACM: Rear hitch draft sensitivity switch circuit fault

The control module has detected an electrical circuit malfunction (such as an open circuit, short to ground, or short to power) in the potentiometer/switch used by the operator to adjust the Electronic Draft Control (EDC) sensitivity.

• MAGNUM AFS Connect
• Puma
• Maxxum
• Steiger

1. 1

   Inspect the physical condition of the draft sensitivity control knob/potentiometer located on the armrest control console to ensure it is not physically broken or jammed.

2. 2

   Access the wiring beneath the armrest panel and inspect the harness and connectors between the draft sensitivity switch and the ACM for chafing, pinched wires, corrosion, or backed-out pins.

3. 3

   Using a multimeter, verify that the potentiometer is receiving the correct 5V reference voltage and a solid ground from the ACM.

4. 4

   Back-probe the signal wire from the potentiometer to the ACM and perform a signal sweep test. Slowly turn the draft sensitivity knob from fully counter-clockwise to fully clockwise; voltage should sweep smoothly without dropouts or spikes.

5. 5

   Look for accompanying codes (e.g., 518685-06 for high voltage, 518685-13 for low voltage, or 518686-02 for a disconnected switch) to help pinpoint if the circuit is shorted or open.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the negative battery cable to prevent electrical shorts during repair.

2. 2

   Access the Armrest Console

   Remove the retaining screws securing the top cover of the armrest control panel to expose the EDC switches and potentiometers.

3. 3

   Disconnect the Switch

   Carefully unplug the electrical connector from the rear hitch draft sensitivity switch.

4. 4

   Repair Wiring

   If the diagnostic checks revealed a broken wire or corroded connector, splice in a new section of wire or replace the damaged connector pin.

5. 5

   Replace the Switch

   If the potentiometer failed the sweep test, unclip or unscrew the faulty switch assembly from the armrest bezel and install the new OEM replacement switch.

6. 6

   Reassembly

   Reconnect the electrical harness to the switch, ensuring the locking tab clicks into place. Reinstall the armrest control panel cover.

7. 7

   Reconnect Power

   Reconnect the negative battery cable.

8. 8

   Clear Codes & Calibrate

   Connect a diagnostic tool (such as the Case IH Electronic Service Tool) to clear the inactive 518687-02 fault code. Depending on the model, you may need to perform a hydraulic lift auto-calibration procedure via the tractor's display monitor to initialize the new potentiometer values.