Smeg oven shows Er18 and the interior temperature seems incorrect compared to the set value.

Safety first: Disconnect power before accessing the sensor or control board.

• Verify with thermometer: Use an accurate oven thermometer to compare actual cavity temperature with the set temperature at several points (e.g., 150°C, 180°C, 200°C).
• Inspect sensor mounting: Ensure the NTC sensor is firmly mounted and not loose or pulled away from the cavity wall.
• Test sensor resistance: Remove and measure the sensor at room temperature and, if possible, at a known elevated temperature (e.g., in warm water). Compare with Smeg specifications. Replace if out of tolerance.
• Calibration: Some Smeg models allow temperature offset adjustment via the user menu or service mode. Apply a small offset if readings are consistently off but sensor is good.
• Control board replacement: If calibration cannot correct the error and the sensor and wiring are good, replace the main control board.