Case IH 518422-03 - ACM – ACM: Hand throttle 1 voltage high

The control module is detecting that the signal voltage from the primary hand throttle position sensor (potentiometer 1) is exceeding the maximum expected threshold (typically above 4.5V - 4.8V). This usually indicates a short to power in the signal wire, an open ground circuit, or an internally failed/misaligned potentiometer.

• MAGNUM AFS Connect
• Steiger AFS Connect
• Optum AFS Connect

1. 1

   Monitor live data using the AFS Pro display or Electronic Service Tool (EST) to see if 'Hand Throttle 1' voltage is pegged at 5V or spikes erratically when the lever is moved.

2. 2

   Inspect the wiring harness and connectors between the potentiometer and the ACM for pinched wires, rubbed insulation causing a short to a 5V/12V source, or a disconnected/corroded ground pin.

3. 3

   Disconnect the sensor and use a multimeter to verify it is receiving a steady 5V reference and has a solid ground.

4. 4

   Measure the resistance across the potentiometer's sweep with a multimeter. If resistance drops to zero or goes infinite unexpectedly, the sensor is internally faulty.

5. 5

   Check mechanical alignment to ensure the potentiometer hasn't physically slipped or rotated out of its mounting bracket, pushing the sweep out of its calibrated range.

1. 1

   Power Down

   Turn off the ignition and disconnect the tractor's battery to prevent electrical spikes.

2. 2

   Access the Sensor

   Remove the retaining screws for the right-hand armrest console cover/trim to expose the internal linkages of the throttle and multi-function handle.

3. 3

   Remove the Faulty Sensor

   Locate the hand throttle potentiometer attached to the base of the throttle lever. Disconnect its 3-pin electrical connector. Remove the mounting screws (usually M4 or M5 hex/torx screws) and pull the sensor off the pivot shaft.

4. 4

   Install the New Sensor

   Slide the new potentiometer onto the throttle lever shaft. Ensure the drive tang/slot on the sensor aligns perfectly with the flat spot or pin on the throttle linkage. Secure it with the mounting screws.

5. 5

   Reassembly

   Reconnect the electrical harness and reinstall the armrest covers. Reconnect the battery.

6. 6

   Calibration (Required)

   Perform a Hand Throttle Calibration via the tractor's display (or EST) so the ACM can learn the new minimum (idle) and maximum (high idle) voltage limits.