Case IH 18253 (518558.02, 518558.07) - ACML – ACML: EHR Encoder Switch ACML - error state

The control module detects an implausible signal, open circuit, or erratic voltage fluctuation from the EHR lever's position sensor (potentiometer). This is primarily caused by poor electrical contact inside the EHR lever due to plastic debris generated by internal friction.

• MAXXUM T4E
• VESTRUM CVX
• Case IH Puma
• Case IH Maxxum
• Case IH Vestrum
• Case IH Magnum
• Case IH Optum

1. 1

   Move the affected EHR lever and feel for excessive physical friction, binding, or grinding, which indicates internal plastic degradation.

2. 2

   Inspect the wiring harness and connectors between the EHR lever panel and the ACML. Look for loose pins, corrosion, or chafed wires that could cause an open circuit or short to ground.

3. 3

   Connect the CNH Electronic Service Tool (EST) and monitor the live voltage data for the EHR lever position. Slowly move the lever through its full range of motion; if the voltage spikes or drops erratically, the potentiometer is contaminated or failed.

4. 4

   Check the current software version of the ACML. Older software versions are highly sensitive to minor voltage fluctuations.

1. 1

   Preparation

   Park the tractor on a level surface, lower all implements, engage the parking brake, and turn off the key switch.

2. 2

   Access the Armrest

   Remove the retaining screws on the Multicontroller armrest console to lift the top cover and access the EHR lever panel.

3. 3

   Remove the Faulty Lever

   Disconnect the electrical harness connector from the affected EHR lever. Remove the mounting hardware securing the lever block to the panel and extract the faulty switch.

4. 4

   Install the New Lever

   Install the updated EHR lever assembly (which features an improved 'Soundwell' potentiometer designed to prevent debris buildup). Secure the mounting hardware and reconnect the harness.

5. 5

   Reassemble

   Reinstall the armrest console cover.

6. 6

   Software Update

   Using the CNH EST, update the ACML software to version 3.0 or 3.1 (or the latest available). The revised software includes updated error code parameters that are more tolerant of minor, non-critical voltage fluctuations.

7. 7

   Calibration

   Perform the EHR valve calibration procedure. This can often be accessed via the tractor's display menu (e.g., the 'HH' menu) or the EST. Calibration is required so the controller learns the new lever's address, limits, and deadbands.