Fendt 0A.1.C2 – MFA (Multifunction Armrest) control module (A039 / A100): A039 / A100 - MFA, multifunction armrest. Faulty MFA button (total lock).

The system has detected a fault with the 'total lock' button located on the multifunction armrest (MFA). The button is likely stuck, shorted, or sending an implausible signal to the control unit. Because the system cannot verify the state of the lock button, total unlocking is not possible, and as a safety precaution, the hydraulic valves remain locked and cannot be operated.

• 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 series
• Fendt 400 Vario series
• Fendt 700 Vario series (COM III, SCR, S4)
• Fendt 800 Vario series
• Fendt 900 Vario series (COM III, SCR, S4)
• Fendt 1000 Vario series

1. 1

   Inspect the total lock button on the multifunction armrest to see if it is physically stuck due to dirt, sticky residue, or mechanical failure.

2. 2

   Turn the tractor off and back on to verify if the button was simply engaged when the ignition was switched on.

3. 3

   Connect the FENDIAS diagnostic tool to monitor the live state of the MFA total lock button, checking for a permanently 'pressed' state or an open circuit/signal fault.

4. 4

   Check the wiring harness and connectors underneath the armrest leading to the A039/A100 module for pinched wires or loose connections.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the battery to prevent electrical shorts while working on the armrest control unit.

2. 2

   Access the MFA Module

   Carefully remove the top cover/housing of the multifunction armrest to expose the internal button matrix and the A039/A100 circuit board.

3. 3

   Clean or Replace the Button

   If the total lock button is simply jammed by debris, clean the housing and the button mechanism thoroughly with electrical contact cleaner. If the microswitch on the board or the physical button is broken, you will need to replace the button set or the affected module.

4. 4

   Reassemble

   Reinstall the armrest cover and ensure all wiring harnesses are securely plugged back into the comfort module.

5. 5

   Clear Codes & Test

   Reconnect the battery, turn on the ignition, and use the tractor's terminal or FENDIAS to clear the 0A.1.C2 fault code. Test the total lock button to ensure the hydraulic valves lock and unlock correctly. (Note: If the internal circuit board is damaged, the entire armrest control module must be sent out for repair or replaced entirely).