Fendt 04.1.25 – A039 MFA (Multifunction Armrest) / A100 MFA: A039 - MFA, multifunction armrest: Joystick signal 'F/R quick reverse' faulty.

The system has detected an invalid, missing, or out-of-range electrical signal from the Forward/Reverse (F/R) quick shuttle button located on the main multifunction joystick, causing the TMS (Tractor Management System) to automatically switch off.

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• Fendt 200 V/F/P Vario
• Fendt 300 Vario (COM III & newer)
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III & SCR)
• Fendt 800 Vario (COM III & SCR)
• Fendt 900 Vario (COM III & SCR)

1. 1

   Inspect the F/R quick reverse button on the joystick for physical damage, sticking, or accumulated dirt/debris that might prevent the switch contacts from closing or opening properly.

2. 2

   Check the internal wiring harness and connectors within the multifunction armrest (between the joystick and the MFA circuit board) for chafing, loose pins, or corrosion.

3. 3

   Test the A039 MFA using the OEM 160-pin adapter box to verify the raw electrical signal coming from the joystick switch.

4. 4

   Clear the code and actuate the switch to see if it immediately returns as an active hard fault.

1. 1

   Preparation

   Park the tractor on a level surface, turn off the ignition, and disconnect the battery to prevent electrical shorts while working on the armrest control board.

2. 2

   Disassembly

   Remove the retaining screws and carefully lift the upper cover of the A039/A100 multifunction armrest to access the base of the joystick and the internal wiring harness.

3. 3

   Component Isolation

   Disconnect the electrical harness connecting the joystick to the armrest's main control board.

4. 4

   Testing/Replacement

   Test the F/R switch continuity directly with a multimeter. If the switch is faulty (and because these switches are often integrated into the joystick circuit board), the multifunction joystick assembly must be replaced.

5. 5

   Installation

   Install the new joystick assembly and securely reconnect the wiring harness to the MFA board.

6. 6

   Reassembly

   Reinstall the armrest covers and secure the screws.

7. 7

   Relearn/Clear

   Reconnect the battery and turn on the ignition. Access the Varioterminal or instrument panel to clear the stored 04.1.25 fault code.

8. 8

   Validation

   Test the forward/reverse quick shuttle function to confirm the tractor changes direction properly and that the TMS remains active without throwing the code again.