Oven takes excessively long to preheat or never reaches set temperature (electric or gas)

Safety first: Turn off power and gas (for gas models) before inspecting internal components. Allow the oven to cool.

• Check door seal: Inspect the oven door gasket for gaps, tears, or compression. Close the door on a sheet of paper; it should hold firmly all around. Replace the gasket if leaking.
• Inspect elements/igniter: For electric ovens, check bake and broil elements for damage and test continuity. For gas ovens, observe ignition time and flame quality; replace a slow or weak igniter.
• Test temperature sensor: Measure resistance of the sensor at room temperature and compare to specifications. Replace if out of range.
• Verify with thermometer: Use an oven thermometer to confirm actual temperature vs setpoint. If consistently low with good components, calibration or control board replacement may be needed.