Fendt 0F.1.29 – A039 - MFA (Multifunction Armrest): A039 - MFA, multifunction armrest. Button, hydraulic circuit 3. Faulty button, signal line fault.

The tractor's electronic system has detected an electrical fault, signal interruption, or physical failure in the button that controls hydraulic circuit 3, located on the multifunction armrest (MFA) joystick. As a safety consequence, the button for hydraulic circuit 3 is rendered inoperable until the next trouble-free cold start.

• 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 300 Vario (COM III)
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III)
• Fendt 800 Vario (COM III)
• Fendt 900 Vario (COM III) (e.g., 916, 920, 924, 926, 930, 936)

1. 1

   Inspect the hydraulic circuit 3 button on the main drive joystick for physical damage, sticking, or debris.

2. 2

   With the engine running, test the signal voltage for hydraulic circuit 3 (should read 14 VDC when operated and 0 VDC when not operated).

3. 3

   Check the internal wiring harness connecting the joystick buttons to the A039 MFA control board for pinched wires or line discontinuities.

4. 4

   Use the Fendt 160-pin adapter box to test the A039 module directly for internal faults.

5. 5

   Turn the tractor off completely and perform a cold start to see if the fault clears, as the system locks the valve out until a trouble-free startup is achieved.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the electric main switch / battery to prevent short circuits.

2. 2

   Access the Joystick

   Carefully disassemble the multifunction armrest (MFA) console to access the internal wiring and the base of the Vario drive joystick.

3. 3

   Test the Switch Plate

   Disconnect the joystick harness and test the specific microswitch for hydraulic circuit 3 for continuity when pressed.

4. 4

   Replace the Component

   If the wiring is damaged, repair the harness. If the button/microswitch on the joystick circuit board has failed, you must either replace the joystick switch plate, replace the entire joystick assembly, or send the joystick to a specialized agricultural electronics repair center to have the internal CAN circuit board and foil buttons repaired.

5. 5

   Reassembly

   Reinstall the joystick and reassemble the multifunction armrest.

6. 6

   Clear Codes

   Reconnect the battery, perform a cold start, and test hydraulic circuit 3 to ensure the fault code 0F.1.29 is cleared and functionality is restored.