Case IH 518423-01 - ACM – ACM: Hand throttle 2 internal failure

The secondary position sensor (potentiometer) for the hand throttle is sending an erratic, missing, or out-of-range signal (typically outside the normal 0.5V to 4.5V operating range). This may limit engine RPM or disable the hand throttle entirely.

• MAGNUM AFS Connect
• Magnum
• Puma
• Steiger
• Optum
• T7
• T8
• T9

1. 1

   Visual Inspection: Remove the armrest cover and inspect the wiring harness connecting the hand throttle to the ACM. Look for pinched wires, chafing, or loose connector pins.

2. 2

   Voltage Supply Test: Disconnect the hand throttle potentiometer and turn the key to the ON position. Verify that the sensor is receiving a steady 5V reference signal and has a solid ground from the ACM.

3. 3

   Signal Sweep Test: Using the Case IH Electronic Service Tool (EST) or the tractor's built-in Instrument Cluster Panel (ICP) diagnostic monitor, observe the 'Hand throttle #2 position' voltage. Slowly move the throttle lever from low idle to high idle. The voltage should scale smoothly without dropping out or spiking. If the voltage is erratic, stuck, or reads 0V/5V, the potentiometer has failed internally.

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Access the ACM

   Remove the retaining screws on the right-hand Multi-Control Armrest console to lift off the upper plastic housing.

3. 3

   Remove the Faulty Sensor

   Locate the hand throttle lever assembly. Disconnect the wiring harness connector leading to the throttle potentiometer.

4. 4

   Dismount the Assembly

   Remove the mounting hardware (typically Torx or Phillips screws) securing the hand throttle lever and potentiometer to the armrest chassis.

5. 5

   Install the New Part

   Mount the replacement throttle potentiometer/lever assembly and secure the hardware. Reconnect the electrical harness.

6. 6

   Reassemble

   Carefully reinstall the armrest console cover, ensuring no wires are pinched in the process. Reconnect the battery.

7. 7

   Calibration

   A new throttle potentiometer must be calibrated so the ACM learns the new minimum (low idle) and maximum (high idle) voltage limits. This can be done via the EST laptop software or through the tractor's ICP display by entering the 'Armrest Calibration' menu, selecting the Hand Throttle, and following the on-screen prompts to move the lever to its physical limits and saving the values.