Fendt A.1.39 – ECU, enhanced control, electric auxiliary control valves: Spool valve fault, valve 3 — Main piston cannot return to neutral position

The main piston inside the 3rd auxiliary control valve (Y017) is physically sticking or failing to return to its center/neutral position due to debris or contamination in the hydraulic oil. This is a critical safety issue that can cause undefined and uncontrolled functions.

• 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
• Fendt 300 Vario (COM III)
• Fendt Farmer 400 Vario (COM III)
• Fendt Favorit 700 Vario (COM III)
• Fendt 800 Vario (COM III)
• 815
• 817
• 818
• Fendt 900 Vario (COM III)
• 916
• 920
• 924
• 926
• 930
• Fendt 711
• Fendt 712
• Fendt 720
• Fendt 722
• Fendt 724

1. 1

   Test the manual actuation of the valve actuator. The actuator must not have any play, and the slider must be able to move to the center (neutral) position by itself.

2. 2

   Inspect the hydraulic oil for visible signs of debris, metal shavings, or severe degradation, which is the root cause of the piston sticking.

3. 3

   Verify if the valve bus has locked out hydraulic functions, as the system will often disable valve operation to prevent uncontrolled movements.

1. 1

   Valve Replacement/Cleaning

   Remove spool valve 3 (Y017). Because internal scoring from contamination usually damages the tight tolerances of the main piston, the selective control valve typically must be replaced.

2. 2

   System Flush

   Drain the contaminated hydraulic oil from the tractor. The hydraulic system must be flushed to ensure no residual debris remains that could immediately damage the new valve.

3. 3

   Filter Replacement

   Replace the main hydraulic filters to capture any remaining particulates.

4. 4

   Refill

   Refill the system with approved hydraulic fluid (e.g., Fendt Super Hyd, Fendt Extra Hyd 68, or STOU SAE 5W-30/10W-40 depending on the exact model and operating hours).

5. 5

   EOL Programming

   After installing a new auxiliary control valve, the tractor's ECU may require EOL (End of Line) programming via FENDIAS/SERDIA diagnostic tools to register the new valve's position on the CAN bus.