Freezer shows F9; may not respond to controls; cooling may stop.

Safety first: Disconnect mains power before opening any electronic compartments.

Steps:

• Power cycle: Unplug the freezer for at least 10 minutes to fully discharge the electronics, then reconnect and observe if F9 clears.
• Check supply voltage: Ensure the outlet provides stable voltage within the range specified on the rating plate. Avoid using undersized extension cords.
• Inspect control board: Remove the top or rear electronics cover and visually inspect the PCB for burnt components, bulging capacitors, or corrosion.

Remedy: If F9 persists after a reset and there is no visible wiring issue, the main control board likely needs replacement or reprogramming. This is typically a technician-level repair because Liebherr boards may require specific configuration for the model.