Fendt 18.1.06 – A039 - MFA, multifunction armrest / A100 - MFA, multifunction armrest: S053 - Switch, driver seat faulty / Signal fault

The system detects that the driver's seat is not 'loaded' (occupied) when steering is activated or when the tractor is stationary and attempting to move. The Tractor Management System (TMS) is switched off and selection of the direction of travel is disabled in accelerator pedal mode when the vehicle is stationary.

• 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)
• Fendt 800 Vario (COM III, SCR, S4)
• Fendt 900 Vario (COM III, SCR, S4)

1. 1

   Connect the FENDIAS diagnostic tool and monitor the live state of the S053 drive switch to see if the signal changes when weight is applied to the seat.

2. 2

   Check the physical seat switch under the seat cushion to ensure it is not mechanically jammed by dirt or debris and that the seat suspension travels enough to actuate the switch.

3. 3

   Inspect the wiring harness leading to the seat, specifically cable coupler X830, for loose pins, corrosion, or wire chafing.

4. 4

   Unplug the switch and use a multimeter to test for continuity across the switch terminals when the seat is occupied versus empty.

1. 1

   Park the tractor on a level surface, apply the parking brake, and turn off the ignition.

   Ensure the tractor is safely parked before beginning work.

2. 2

   Disconnect the battery.

   Disconnect the battery to prevent accidental short circuits while working on the seat wiring.

3. 3

   Remove the driver's seat cushion.

   Usually held by clips or a few bolts at the front/bottom of the seat frame, remove it to access the inner suspension components.

4. 4

   Locate the S053 seat switch assembly.

   Find the switch mounted on the suspension frame.

5. 5

   Disconnect the electrical plug.

   Disconnect the plug connecting the switch to the tractor's cab harness.

6. 6

   Unbolt or unclip the faulty switch.

   Remove the switch from its mounting bracket.

7. 7

   Install the new OEM seat switch.

   Secure it in the exact same orientation as the old switch.

8. 8

   Reconnect the electrical harness and reinstall the seat cushion.

   Ensure all connections are secure and the cushion is properly reattached.

9. 9

   Reconnect the battery and turn on the ignition.

   Restore power to the tractor.

10. 10

    Clear the stored 18.1.06 fault code.

    Use the tractor terminal or FENDIAS software to clear the code.

11. 11

    Test the repair.

    Sit in the seat, select a travel direction in accelerator pedal mode, and verify that the tractor engages the transmission without throwing the fault code.