Case IH 18334 (4169.02, 4169.03, 4169.04, 520624.07) - ACML – ACML: MFH Second Function Switch Error State

The control module is detecting an implausible signal, an open circuit, or a short circuit from the MFH Second Function Switch (the black button on the front of the Multi-Function Handle).

• MAXXUM T4E
• VESTRUM CVX
• Case IH Magnum Series (e.g., Magnum 235, 260, 280, 290, 340 - Tier 4A CVT and Powershift models)
• Case IH Steiger Series (e.g., Steiger 400, 425, 450 Quadtrac)
• Other models utilizing the AFS Pro 1200 or Pro 700 displays with the MultiControl Armrest

1. 1

   Inspect the Second Function Switch (the black button on the front of the MFH) for physical damage, debris, or sticking.

2. 2

   Check the display for related ACM communication errors (e.g., 2818 - Loss of communication with the Armrest Control Module) or MFH basic assurance test errors (e.g., 18065 - MFH basic assurance test error) which could indicate a broader harness failure rather than an isolated switch failure.

3. 3

   Verify if the button functions during the 20-second startup window for transmission calibration, as outlined in the Vision Pro Operating System Guide. If it fails to trigger the calibration menu, the switch is unresponsive.

4. 4

   Check the wiring harness and connectors between the Multi-Function Handle and the Armrest Control Module for continuity, pinched wires, or corrosion.

1. 1

   Disconnect battery power

   Disconnect battery power before servicing the armrest controls to prevent short circuits.

2. 2

   Disassemble MFH

   Disassemble the MFH bezel and handle casing to access the internal switches.

3. 3

   Inspect button cap and microswitch

   Inspect the button cap and the underlying microswitch mechanism.

4. 4

   Replace MFH assembly

   If the switch itself has failed internally, Case IH OEM procedures typically require replacing the entire Multi-Function Handle (MFH) assembly, as the internal circuit board is often serviced as a single unit.

5. 5

   Install new MFH assembly

   Install the new MFH assembly and reconnect the harness to the ACM.

6. 6

   Perform calibration

   Power on the tractor and perform the MFH and Transmission Calibration procedures using the AFS Pro display (pressing the new Second Function button within 20 seconds of startup to initiate calibration).