Fendt 04.1.77 – A039 - MFA (Multifunction Armrest) / A100: A039 (or A100 on some models) - MFA, multifunction armrest. Joystick acceleration rate I…IV.

The system has detected a 'Signal fault' from the joystick's acceleration rate switch. The tractor loses the ability to switch between acceleration rates normally and defaults to an emergency mode where only acceleration rate III is available.

• 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
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III, SCR)
• Fendt 800 Vario (COM III)
• Fendt 900 Vario (COM III, SCR)

1. 1

   Verify Emergency Mode: Confirm that the tractor is locked into acceleration rate III. If it is not, there may be a broader CAN communication issue.

2. 2

   Physical Inspection: Inspect the acceleration rate switch on the joystick for physical damage, sticking, or debris preventing proper contact.

3. 3

   Wiring and Connections: Check the wiring harness and connectors between the joystick and the MFA control board for loose pins, corrosion, or chafing.

4. 4

   Diagnostic Software (FENDIAS): Use Fendt's diagnostic software to monitor the live state of the acceleration rate switch to see if the signal is erratic, stuck open, or stuck closed.

1. 1

   Safety First

   Turn off the tractor, engage the parking brake, and disconnect the battery earth strap to prevent electrical shorts.

2. 2

   Access the Joystick

   Remove the retaining screws on the multifunction armrest cover to access the internal joystick assembly and wiring.

3. 3

   Component Testing/Removal

   Disconnect the joystick wiring harness. If the physical switch is broken, it can sometimes be replaced individually. However, if the internal CAN circuit board has failed, the entire joystick lever must be removed.

4. 4

   Replacement or Refurbishment

   Install the replacement switch or refurbished joystick assembly. (Note: Many dealers and specialists recommend sending the joystick to specialized mechatronics repair services).

5. 5

   Reassembly

   Reconnect the wiring harness and reinstall the armrest cover.

6. 6

   Clear Fault Codes

   Reconnect the battery. Clear the fault code using the tractor's multi-display (by pressing buttons A, B, and C simultaneously) or via the FENDIAS tool.

7. 7

   Calibration

   If a new joystick or potentiometer was installed, perform the required calibration procedures (e.g., Code 4010 for the joystick sliding switch/accelerator pedal range) via the tractor's terminal.