Fendt 05.1.93 – MFA (Multifunction Armrest) module: A039 - MFA, multifunction armrest: Button, front auto mode - Faulty button, Signal fault.

The system has detected an electrical signal fault (such as a short circuit, open circuit, or a mechanically stuck switch) specifically originating from the "front auto mode" button located on the tractor's multifunction armrest.

• 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)
• FENDT 700-900 SCR series (2011.09 and newer)

1. 1

   Inspect the 'front auto mode' button on the armrest for physical damage, sticking, or debris/liquid spills.

2. 2

   Monitor live data using the tractor's terminal or FENDIAS software to see if the button registers as permanently pressed or unresponsive.

3. 3

   Test the A039 MFA electrical connections using a 160-pin adapter box, checking the wiring harness and main connector (X1401) for continuity, corrosion, or loose pins.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical shorts while working on the armrest CAN bus components.

2. 2

   Disassemble the MFA

   Remove the retaining screws on the underside of the multifunction armrest to separate the upper housing.

3. 3

   Inspect Internal Contacts

   Carefully lift the keypad/button matrix. Inspect the printed circuit board (PCB) and the rubber membrane contacts for the front auto mode button. Clean any moisture, dust, or sticky residue using electrical contact cleaner.

4. 4

   Replace Component

   If the button's microswitch or the membrane is physically broken or the signal fault persists after cleaning, the faulty keypad module (or the entire MFA unit, depending on the specific model's parts breakdown) must be replaced.

5. 5

   Reassembly

   Seat the new module or cleaned components back into the armrest housing and secure the casing. Reconnect the main MFA wiring harness.

6. 6

   Clear Fault Codes

   Reconnect the battery and turn on the ignition. Access the fault code menu on the terminal. Press the confirmation button repeatedly until the fault symbol flashes and clears from the active display.

7. 7

   Operational Test

   Test the front auto mode function to ensure the signal is being received by the basic control unit (A050) without triggering a new fault.