Oven displays E3 during preheat and stops heating; temperature overshoots or is unstable.

Safety first: Turn off power at the breaker and allow the oven to cool completely before inspection.

Steps to check:

• Verify ventilation: Ensure the oven has proper clearance around it and that ventilation slots are not blocked by cabinetry or objects. Poor airflow can cause overheating and trigger E3.
• Check temperature sensor: Access the cavity sensor and measure its resistance at room temperature. Compare with expected values. If significantly off, replace the sensor.
• Inspect control board relays: With power disconnected, remove the control panel and visually inspect the main PCB. Look for relays with burnt or melted plastic, or signs of arcing. A relay stuck closed can cause continuous heating.
• Check wiring to heating elements: Inspect for shorted wires that might bypass control, especially around the top and bottom elements.
• Replace faulty parts: If the sensor is within spec and wiring is intact, but the oven overheats, the main control board (with its relay drivers) is likely faulty and should be replaced with an OBH Nordica-compatible PCB.
• Test: After replacing components, run the oven at a moderate temperature (e.g., 180°C) and monitor with an oven thermometer to confirm stable temperature and no E3 error.

Warning: Overheating can damage insulation and wiring. If you smell burning or see smoke, disconnect power immediately and have the oven inspected by a professional.