Hansa oven displays E17 and the cavity temperature does not match the set temperature; food undercooks or overcooks.

Safety first: Turn off power before accessing internal components.

• Verify actual temperature: Use an accurate oven thermometer placed in the center of the cavity. Compare the reading to the set temperature at several points (e.g., 150°C, 180°C, 220°C).
• Check sensor resistance curve: Measure the NTC sensor resistance at room temperature and at a known elevated temperature (e.g., 100°C using boiling water if accessible). Compare to Hansa specifications. Replace the sensor if readings are out of range.
• Sensor mounting: Ensure the sensor is firmly mounted and not touching metal parts that could skew readings.
• Calibration (if available): Some Hansa models allow temperature offset calibration via the settings menu. Adjust according to the user manual if the deviation is small and stable.

When to call a technician: Large or erratic deviations after sensor replacement suggest a control board issue requiring professional service.