Fendt 08.1.34 – Rear EPC (Electronic Power Control): A035 - Rotary switch, rear power lift, "lowering speed"

The fault indicates an issue with the lower potentiometer (the rotary knob used to adjust the lowering speed of the rear linkage). The system is not receiving a valid signal from this switch. Modifications to the rear power lift lowering speed can no longer be made. The system will lock the current setting or default to a safe baseline.

• 309 Vario COM III
• 310 Vario COM III
• 311 Vario COM III
• 312 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)

1. 1

   Inspect the A035 rotary switch on the right-hand control console. Check if the knob is physically broken, sticking, or spinning freely without resistance.

2. 2

   Connect the FENDIAS diagnostic tool and monitor the live data for the 'lowering speed' potentiometer. Turn the knob from minimum to maximum to see if the voltage/percentage changes smoothly. If the value is stuck or erratic, the potentiometer is faulty.

3. 3

   Access the underside of the EPC control panel. Inspect the wiring harness and connectors going to the A035 switch for loose pins, corrosion, or chafed wires.

4. 4

   Verify that the potentiometer is receiving the correct reference voltage (typically 5V or 9.5V depending on the exact EPC board version) and has a good ground.

1. 1

   Power Down

   Turn off the tractor and disconnect the negative battery terminal to prevent electrical shorts.

2. 2

   Access the Panel

   Carefully pry up or unscrew the trim surrounding the right-hand EPC control console to expose the underside of the control panel.

3. 3

   Disconnect Harness

   Unplug the electrical connectors attached to the A035 rotary switch / EPC control board.

4. 4

   Remove the Switch/Board

   Depending on the specific Vario model, if the A035 potentiometer is an individual switch, unbolt the retaining nut under the knob and swap the potentiometer. If it is integrated, remove the entire EPC control panel board for replacement or send it to an agricultural electronics specialist for board-level repair.

5. 5

   Reassembly

   Install the new switch or repaired board, reconnect the wiring harness, and snap the console trim back into place.

6. 6

   Reconnect Battery & Clear Codes

   Reconnect the battery. Turn the ignition on and use the tractor's terminal or FENDIAS to clear the stored 08.1.34 fault code.

7. 7

   Calibration

   Test the rear power lift. Note that some EPC potentiometer replacements require an End-of-Line (EOL) calibration (e.g., calibration code 8001) via the tractor's terminal so the ECU can learn the new minimum and maximum resistance values.