Fendt A.1.DD – Working and Steering Hydraulics / General System: Front external key (pushbutton) actuates twice or the key is physically/electrically stuck

The front power lift cannot be lowered properly, or no valve operation is available for the front lift due to a double button operation or a stuck button on the external front power lift controls (S021 or S022).

• 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
• 300 Vario (COM III)
• 400 Vario (COM III) (e.g., 409, 410, 411, 412, 415)
• 500 Vario (e.g., 516)
• 700 Vario (COM III) (e.g., 711, 712, 714, 716)
• 800 Vario (COM III) (e.g., 815, 817, 818)
• 900 Vario (COM III & S4) (e.g., 916, 920, 924, 926, 930, 933, 936, 939)

1. 1

   Inspect the external front power lift pushbuttons (S021 for raise, S022 for lower) for physical damage, dirt, or debris causing them to bind or stick.

2. 2

   Inspect the wiring harness and connections for the switches (Spool valves 2 circuit) for shorts to ground or broken wires.

3. 3

   Test voltage inputs at the switch with ignition ON: not actuated should read approximately 3.7 VDC, actuated should read approximately 1.8 VDC. A reading of 1.8 VDC without pressing indicates an internally shorted or stuck switch.

1. 1

   Clean switch area

   Clean the area around the external front power lift switches (S021 and S022) to ensure no mud or debris is causing physical binding.

2. 2

   Remove faulty switch

   If cleaning does not resolve the issue and the switch fails the voltage test (or is permanently stuck), disconnect the battery and remove the faulty switch (S021 or S022) from its external mounting housing.

3. 3

   Clean harness connections

   Clean all harness connections thoroughly before installation.

4. 4

   Apply dielectric grease

   Apply dielectric grease to the new switch connections to prevent future corrosion from dust, mud, and moisture.

5. 5

   Install new switch

   Install the new direct-replacement switch.

6. 6

   Test operation

   Reconnect the battery, clear the fault codes via the terminal, and test the front power lift operation from the external buttons to confirm the repair.