Fendt 18.1.03 – A039 - MFA (Multifunction Armrest): A039 - MFA, multifunction armrest fails to report

Loss of CAN bus communication between the multifunction armrest and the tractor's central network. The system is no longer receiving signals from the armrest, which controls critical functions like the Vario transmission, working hydraulics, PTO, and Tractor Management System (TMS).

• 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 & SCR models)
• Fendt 800 Vario (COM III)
• Fendt 900 Vario (COM III & SCR models)
• Fendt 922
• Fendt 924
• Fendt 927
• Fendt 930
• Fendt 933
• Fendt 936

1. 1

   Test the A039 module using the Fendt 160-pin adapter box to isolate the module from the rest of the harness.

2. 2

   Check the CAN bus wiring connection between the A039 MFA and the A050 (basic control unit) for continuity, shorts, or open circuits.

3. 3

   Verify that the A039 module is receiving proper +supply voltage and has a solid ground connection.

4. 4

   Verify the driver seat switch (S053), as seat switch signal faults (e.g., code 18.1.06) are closely tied to the armrest circuit and can interrupt operation.

1. 1

   Inspect Wiring

   Access the wiring harness routed to the multifunction armrest. Look for pinched wires, chafing, or disconnected plugs. Repair any damaged wiring or pins.

2. 2

   Module Replacement

   If the wiring, power, and ground are all verified as good but the MFA still fails to report to the bus, the internal hardware of the A039 module has failed and the armrest unit must be replaced.

3. 3

   EOL Programming

   If a new A039 MFA is installed, it must be calibrated and programmed to the tractor's network using FENDIAS diagnostic software so it can communicate with the A050 basic control unit.