Case IH 18271 (518757.03, 518757.04) - ACML – Armrest Control Module (ACML): Rear Hitch Position Control Potentiometer Error
Issue description
The fault indicates an error state with the Rear Hitch Position Control Potentiometer, typically manifesting as a voltage irregularity in the sensor circuit (voltage too low indicating a short to ground/open circuit, or voltage too high indicating a short to power/disconnected ground).
Applies to these machines
13 machines- MAXXUM T4E
- VESTRUM CVX
- Case IH Magnum 235
- Case IH Magnum 260
- Case IH Magnum 290
- Case IH Magnum 315
- Case IH Magnum 340 (Series 4)
- Case IH Puma 165
- Case IH Puma 180
- Case IH Puma 195
- Case IH Puma 210
- Case IH Puma 225 CVX
- Case IH Vestrum 100 CVX
Check the cause
Inspect the wiring harness and connectors between the ACML (Armrest) and the rear hitch position control potentiometer for physical damage, corrosion, or loose pins.
Check the signal voltage coming from the potentiometer: if reading below the minimum threshold, suspect a 'voltage too low' condition (open/short to ground); if reading above the maximum threshold, suspect a 'voltage too high' condition (short to power/bad ground).
Test the potentiometer's resistance sweep to see if there are dead spots or an internal failure.
Repair steps
Access component
Access the armrest control console (ACML) where the rear hitch position control potentiometer is located.
Disconnect power
Disconnect the battery or turn off the ignition to prevent electrical spikes.
Disconnect harness
Disconnect the wiring harness from the faulty potentiometer.
Remove component
Remove the retaining hardware and extract the failed potentiometer.
Install component
Install the new rear hitch position control potentiometer and secure it.
Reconnect harness
Reconnect the wiring harness.
Clear faults
Power on the machine and use the Electronic Service Tool (EST) to clear the logged fault codes.
Calibrate system
Recalibrate the rear hitch system and the armrest controls so the ACML learns the minimum and maximum voltage values of the new potentiometer.
Parts you might need
(1)Rear Hitch Position Control Potentiometer
Ensure you are ordering the 'Position Control' potentiometer, as the armrest also contains separate potentiometers for 'Draft Control', 'Height Limit', and 'Drop Rate' which may look similar but serve different functions.
Get help to fix this fault by requesting a quote
