Microwave beeps and shows F3; unit may not start or may stop mid-cycle.

Safety first: Unplug the microwave before any disassembly. Avoid contact with high-voltage components.

• Step 1 – Clean the cavity: Grease and food vapors can coat the humidity sensor. Thoroughly clean the interior with a mild detergent and soft cloth, especially near the sensor grill (often on the top or side wall).
• Step 2 – Power reset: After cleaning, leave the door open to dry, then unplug for 5 minutes and reconnect. Test a short heating cycle.
• Step 3 – Inspect humidity sensor: If accessible, locate the humidity sensor module (often behind a small grill inside the cavity or behind the control panel). Check for obvious damage or loose connectors.
• Step 4 – Reseat connector: With power disconnected, unplug and replug the sensor connector to ensure a solid connection.
• Step 5 – Replace sensor: If F3 persists, replace the humidity / steam sensor module with the correct Bauknecht part.
• Step 6 – Control board: If a new sensor does not resolve the issue, the main control board may be defective and should be replaced by a technician.