Fendt 05.1.97 – A050 - ECU, Basic Control Unit: S075 - Switch, guard rail pump flow monitor

The flow monitor is reporting a failure of the guard rail pump (wheel-driven emergency steering pump). During forward travel at speeds greater than 16 km/h, the return voltage signal from the switch must be > 1.1 V. If it drops below this threshold, the system logs this fault and limits hydraulic flow to 5 liters/minute for each installed spool valve.

• 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 500 Vario (S4)
• Fendt 700 Vario (COM III, SCR, S4)
• Fendt 800 Vario (COM III, S4)
• Fendt 900 Vario (COM II, COM III, SCR, S4) (e.g., 922, 924, 927, 930, 933, 936, 939)
• Fendt 1000 Vario

1. 1

   Verify that the A050 Basic Control Unit is supplying the correct basic signal voltage of 6.0 VDC to the S075 switch.

2. 2

   Monitor the return voltage from the S075 switch. Drive the tractor forward at a speed greater than 18 km/h; the voltage must rise above 1.1 V.

3. 3

   Perform a plausibility check: When the tractor is stationary or driving in reverse, the voltage must be < 1.1 V.

4. 4

   Inspect the wiring harness and separation points for the S075 switch for chafing, corrosion, or open circuits.

5. 5

   Physically test the flow and pressure of the wheel-driven safety steering pump to rule out a mechanical pump failure.

1. 1

   Locate the Switch

   The S075 switch is generally located on the right side of the tractor at the central valve block. Detach the protective cover to access the separation point (e.g., connector X1499).

2. 2

   Test the Circuit

   Disconnect the switch and test the harness side for the 6.0 VDC reference voltage from the A050 ECU.

3. 3

   Replace the Switch

   If the wiring is intact, the pump is generating proper flow, but the switch fails the dynamic/plausibility voltage checks, the S075 switch is internally faulty and must be replaced.

4. 4

   Repair the Pump

   If the switch is working correctly but the pump is not generating flow at speeds > 16 km/h, remove and rebuild or replace the wheel-driven safety steering pump.

5. 5

   Clear Codes

   Reconnect all components, clear the fault codes from the A050 ECU, and test drive the tractor above 20 km/h to ensure the code does not return and spool valve flow restrictions are lifted.