Fendt 4.1.78 – Transmission Control Unit / Basic Control Unit (A050 ECU): S053 - Seat switch — Signal fault from seat switch

The driver presence switch (located inside the driver's seat) is sending an invalid, missing, or implausible signal to the tractor's control system. Because the system cannot verify that the operator is in the seat, the selection of the direction of travel is automatically disabled in accelerator pedal mode when the vehicle is stationary for more than 3 seconds.

• 409 Vario
• 410 Vario
• 411 Vario
• 412 Vario
• 711 Vario
• 712 Vario
• 714 Vario
• 715 Vario
• 716 Vario
• 717 Vario
• 718 Vario
• 916 Vario
• 920 Vario
• 924 Vario
• 926 Vario
• 930 Vario
• 411 Vario COM III
• 412 Vario COM III
• 413 Vario COM III
• 414 Vario COM III
• 415 Vario COM III
• 712 Vario COM III
• 714 Vario COM III
• 716 Vario COM III
• 718 Vario COM III
• 818 Vario COM III
• 820 Vario COM III
• Fendt Farmer 400 series
• Fendt Favorit 700 series
• Fendt Favorit 900 series
• Fendt 300 Vario series
• Fendt 400 Vario series
• Fendt 700 Vario series
• Fendt 800 Vario series
• Fendt 900 Vario series

1. 1

   Connect the FENDIAS diagnostic program and run test A034 (Check drive switch) to monitor the live state of the S053 seat switch.

2. 2

   Inspect the wiring harness beneath the seat. Specifically, check the X830 cable coupler, which houses the connections for both the M007 seat compressor and the S053 seat switch. Look for pinched wires, corrosion, or a loose plug.

3. 3

   Test the seat switch itself with a multimeter. It is a standard NO/NC (Normally Open / Normally Closed) contact switch. Verify that the circuit opens and closes properly when weight is applied and removed from the seat cushion.

1. 1

   Preparation

   Park the tractor on a level surface, turn off the ignition, and disconnect the battery to prevent accidental short circuits.

2. 2

   Access the Switch

   Remove the seat cushion or access the lower suspension base of the driver's seat (Fendt tractors typically use Grammer air suspension seats like the MSG95 or MSG97).

3. 3

   Disconnect Wiring

   Locate the S053 seat switch and disconnect it from the X830 cable coupler.

4. 4

   Remove the Faulty Switch

   Unclip or unscrew the faulty switch from its mounting bracket within the seat frame.

5. 5

   Install the New Switch

   Snap or screw the replacement switch into the factory mounting position.

6. 6

   Reconnect and Reassemble

   Plug the switch back into the X830 coupler and reinstall the seat cushion/bellows.

7. 7

   Clear Codes and Test

   Reconnect the battery, turn on the ignition, and clear the stored 4.1.78 fault code using the FENDIAS tool. Sit in the seat and test the tractor in accelerator pedal mode to ensure the travel direction preselection remains active when stationary.