CLAAS Id7878h / 7878h – MFT (A30): Brightness sensor of the terminal is out of service

The ambient light sensor has failed or lost communication, causing the automatic brightness control of the display terminal to become inactive. The system defaults to a degraded mode where manual brightness control is required.

• CLAAS Axion 800 series (e.g., 810, 820, 830, 840, 850)
• CLAAS Axion 900 series (e.g., 920, 930, 940, 950)
• CLAAS Arion 500 and 600 series (e.g., 510, 640)
• CLAAS Lexion combines equipped with the CEBIS display

1. 1

   Verify if the terminal screen is still functional by attempting to adjust the brightness manually

2. 2

   Check the connectors and continuity of the harnesses linking the MFT (A30) component to the vehicle's CAN bus

3. 3

   Check the sources of energy to the CEBIS terminal, including fuses, power supply lines, and ground connections

4. 4

   Inspect the wiring harness at the back of the terminal for any short-circuits, open circuits, or damaged pins

1. 1

   Isolate the Fault

   Perform the manual brightness check. If the operator is satisfied with manually adjusting the screen brightness, no immediate repair is strictly necessary, as this is a non-critical convenience failure.

2. 2

   Inspect Connections

   Power down the machine and remove the rear cover of the CEBIS terminal. Disconnect the main harness and inspect for corrosion or pushed-out pins. Clean with contact cleaner and reconnect.

3. 3

   Check Fuses

   Verify the terminal module power supply fuses (e.g., "Cébis MFT" power supply fuse) are intact and providing proper voltage.

4. 4

   Replace the Terminal

   Because the brightness sensor is an internal component of the CEBIS MFT (A30) display, it cannot be serviced separately in the field. If the wiring is good and the automatic brightness function must be restored, the entire CEBIS terminal must be replaced or sent to an agricultural electronics specialist for internal board repair.

5. 5

   Clear Codes

   After installing a new or remanufactured terminal, turn on the ignition, verify that automatic brightness functions correctly, and clear the Id7878h fault code from the system memory.