Fendt 0A.1.BB – MFA (Multifunction Armrest) / A039 / A100: Linear module 3 (rocker switch) is faulty or engaged during startup

Linear module 3 (rocker switch) is faulty or was physically engaged/actuated when the tractor's ignition was switched on. The corresponding hydraulic valve position will not function, and the system will lock the valve 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
• 919 Vario COM III
• 925 Vario COM III
• 928 Vario COM III
• 931 Vario COM III
• 934 Vario COM III
• 700 Vario SCR series
• 200 Vario series
• 300 Vario series
• 400 Vario series
• 500 Vario series
• 800 Vario series
• 1000 Vario series

1. 1

   Visually and physically inspect Linear module 3 (3rd hydraulic rocker switch) to ensure it is not stuck, jammed by debris, or being accidentally pressed

2. 2

   Perform an ignition cycle test by turning the tractor off, ensuring the switch is in the neutral/center position, and turning the ignition back on without touching the armrest

3. 3

   Check for accompanying fault codes, specifically 0A.1.BA, which indicates Linear module 3 has lost its calibration

4. 4

   Use FENDIAS diagnostic software to monitor the live state of the MFA switches to see if the module is continuously sending an engaged signal despite being physically neutral

1. 1

   Clean the Module

   If the rocker switch is sticking, use electrical contact cleaner and compressed air to clear out dust, dirt, or spilled liquids from the edges of the linear module.

2. 2

   Recalibrate the MFA

   If the switch moves freely but throws the code, attempt to recalibrate the multifunction armrest via the tractor's Varioterminal. The specific calibration code for Linear module 3 is '1005'.

3. 3

   Replace the Switch/Module

   If cleaning and calibration fail, the internal potentiometer or return spring of the linear module is broken. Disassemble the armrest console and replace the specific rocker switch/linear module.

4. 4

   Component-Level Repair (Alternative)

   Utilize specialized agricultural electronics repair services (such as Ilgenfritz Mechatronics) to rebuild the MFA and replace the faulty linear module circuit boards.