Case IH 518688-02 - ACM – ACM (Armrest Controller Module): Rear hitch max depth switch circuit fault

The control module is receiving an erratic, out-of-range, or illogical voltage signal from the potentiometer/switch that sets the maximum depth (or lower limit) for the rear 3-point hitch.

• MAGNUM AFS Connect
• Case IH Magnum Series
• Case IH Maxxum Series

1. 1

   Check for accompanying 5-volt reference codes (e.g., Hitch 1014/1015) or CAN communication codes (e.g., Hitch 1012). If the 5V reference has failed, multiple armrest sensors will drop out.

2. 2

   Inspect the wiring harness and connectors under the armrest console. Look for loose, backed-out, or broken pins at the max depth switch connector, and perform a pin drag test to ensure tight contact.

3. 3

   Back-probe the switch circuit to verify it receives a steady 5V reference and a good ground. The signal wire should output a smooth, linear voltage (typically 0.10V to 4.85V DC) as the dial/switch is moved. Drops to 0V or erratic spikes indicate an internal dead spot.

4. 4

   Disconnect the switch and the ACM connector to test harness continuity. Ohm out the signal, power, and ground wires to check for high resistance, an open circuit, or a short to ground.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery ground to prevent electrical shorts while working inside the armrest.

2. 2

   Access the ACM / Console

   Remove the retaining screws securing the top cover or side panel of the operator's armrest console to expose the internal wiring and switches.

3. 3

   Remove the Faulty Switch

   Disconnect the electrical pigtail from the max depth switch. Remove the retaining nut or mounting clips holding the switch/dial assembly to the console bezel.

4. 4

   Install the New Component

   Seat the new switch into the console, secure the retaining hardware, and plug in the electrical connector.

5. 5

   Reassemble and Power Up

   Reinstall the armrest covers and reconnect the battery.

6. 6

   Perform Hitch Calibration

   Recalibrate the hitch system so the ACM can learn the new minimum and maximum voltage limits of the new sensor. This is usually done via the tractor's display monitor or by following the specific hitch calibration sequence for your model (e.g., cycling the hitch up/down switches while the engine is running).