Fendt 0A.1.FC – A050 basic control unit ECU: S067/S068 - Switch (external), valve actuation, raise/lower: Double actuation, faulty button, signal fault

The system is detecting that both the 'raise' and 'lower' external valve actuation buttons are being pressed at the exact same time (often due to a physically stuck button), or there is an electrical fault such as a short circuit in the signal line. When this fault is active, external valve actuation is disabled for safety.

• 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 200 V, F, P, and S Vario series
• Fendt 300 Vario (COM III)
• Fendt 400 Vario (COM III) (e.g., 409, 410, 411, 412)
• Fendt 700 Vario (COM III & S4) (e.g., 711, 712, 714, 716)
• Fendt 800 Vario (COM III & S4) (e.g., 815, 817, 818, 822, 824, 826, 828)
• Fendt 900 Vario (COM III & S4) (e.g., 916, 920, 924, 926, 930, 933, 936, 939)

1. 1

   Visual & Physical Inspection: Check the S067 and S068 external buttons on the rear mudguard/fender. Look for dirt, debris, or physical damage causing the buttons to stick in the depressed position ('double button operation').

2. 2

   Resistance Testing: Disconnect the switch. Switch open (not pressed): Resistance should be infinite. Switch closed (pressed): Resistance should be approximately 0 ohms.

3. 3

   Voltage Testing: With the ignition ON, measure the signal voltage at the switch pins: Switch open (not actuated): The signal voltage should read 6.1 VDC (Note: some specific 900-series manual revisions may show 3.7 VDC depending on the exact pin tested). Switch closed (actuated): The signal voltage should drop to 0 VDC (or 1.8 VDC on certain pins).

4. 4

   Wiring Harness Check: If the switch tests fine mechanically and electrically, inspect the wiring harness between the fender switches and the A050 ECU for chafing, breaks, or shorts to ground.

1. 1

   Turn off the tractor ignition and disconnect the battery to prevent short circuits.

2. 2

   Locate the S067/S068 external valve actuation switches on the rear fender.

3. 3

   Clean the area around the switches thoroughly.

   If a button is simply jammed by mud or debris, freeing it and cleaning the housing may clear the fault code.

4. 4

   If the switch failed the multimeter diagnostic checks, disconnect the wiring harness connector from the back of the switch assembly.

5. 5

   Unbolt or unclip the faulty switch assembly from the fender housing.

6. 6

   Install the new external valve actuation switch assembly and secure it to the fender.

7. 7

   Reconnect the wiring harness, ensuring the weather-tight seal is intact.

8. 8

   Reconnect the battery, turn the ignition ON, and test the external raise/lower functions to ensure the 0A.1.FC code has cleared and functionality is restored.