E12 appears; unit may not respond to temperature changes or may over/underheat.

Safety first: Unplug the Klarstein air fryer and let it cool.

Steps:

• 1. Verify correct parts: If a sensor was recently replaced, confirm that the installed NTC matches the original Klarstein specification (resistance curve and temperature rating). Using a generic sensor can trigger range errors.
• 2. Check sensor mounting: Ensure the NTC sensor is firmly attached to the metal surface or bracket specified by the manufacturer. Poor contact can cause inaccurate readings. Re-secure with the original clip or high-temperature thermal compound if used.
• 3. Inspect wiring and connectors: Look for high-resistance connections (loose plugs, corroded pins) between the sensor and control board. Clean and reseat connectors.
• 4. Compare temperature: With the unit running at a known setpoint (e.g., 180°C), use an external oven thermometer in the basket to compare actual temperature to the display. Large discrepancies may indicate a calibration or board issue.
• 5. Replace control board: If sensors and wiring are correct and E12 persists, the control board's ADC or firmware may be faulty. Replace the main control PCB with the correct Klarstein part.
• 6. Test operation: After reassembly, run several cycles at different temperatures to confirm stable and accurate heating.

Warning: Do not attempt to modify firmware or calibration values unless you have official Klarstein service documentation.