Oven does not reach set temperature; preheat takes excessively long or never completes.

Safety first: Disconnect electrical power and shut off gas (for gas models) before removing panels or burner covers.

• 1. Verify with an oven thermometer: Place a reliable thermometer in the center of the oven and compare actual temperature to the set point after 20–30 minutes.
• 2. Inspect heating elements: For electric La Cornue ovens, visually inspect both the lower bake and upper/convection elements for cold spots or discoloration. During a preheat cycle (with panels in place and using proper safety), observe whether all elements glow evenly. Replace any element that does not heat uniformly.
• 3. Test element resistance: With power off, remove rear or bottom panels to access element terminals. Measure resistance; an element with significantly higher resistance than specification may heat weakly and should be replaced.
• 4. Gas models – check burner flame: Remove the oven base panel to view the burner. The flame should be blue and even along the burner. Yellow, lazy, or small flames indicate a gas pressure or orifice issue. Clean the burner ports and verify the gas regulator and orifice are correct for the fuel type (natural gas vs LPG).
• 5. Check sensor/thermostat: If elements and burner are correct, test the oven sensor or mechanical thermostat for calibration. Replace if readings are out of range or if the thermostat does not respond correctly.