Is your oven taking longer to cook your food than it should? Have you been following all cooking instructions, selecting the correct temperature, and leaving your food in for exactly the amount of time specified, only to discover that everything is still lukewarm and half-raw when you open the door? If you constantly have to put your dinner back in the oven for a few more minutes to get it fully cooked, there's a problem with your appliance that needs to be addressed.
Let's look at some possible causes of your oven, not heating.
Check the breaker
Ovens consume a lot of electricity for cooking and baking, and even a minor power surge can trip the breaker. Look for a breaker labeled "Oven" in your home's service panel; if the breaker has tripped, the switch will be halfway between the "On" and "Off" positions. Push the switch to "Off" and then back to "On" to reset the breaker; however, contact an electrician if the breaker trips again; you may need another electrical circuit or breaker installed.
Check the position of the oven and stove knobs
If you recently removed the knobs while cleaning an oven-range combo with manual knobs instead of a touchscreen, there's a good chance they were reinstalled incorrectly. First, check that each knob is in its proper location; consult your owner's manual if in doubt. Sometimes the solution is as simple as relocating knobs to their correct locations.
Check that the door lever is in the “Unlocked” position
Many self-cleaning ovens have a lever that locks the door during the cleaning process. If the lever is in the "Locked" position, the oven door may not close completely, allowing hot air to escape and slowing down the cooking process.
Check the temperature difference
Even brand new ovens can be off by a few degrees. First, put an oven thermometer in the middle of the center rack to see if your ranges are off. Next, preheat the oven to 300 degrees Fahrenheit and check the temperature with a thermometer after 10 to 15 minutes. Repeat the test. If the thermometer consistently reads 25 degrees lower on each test, it's possible that your oven cooks at a lower temperature than indicated.
Check the heating element
To begin, check the heating element, which is the curved rod that runs along the bottom of the oven. Preheat the oven to 400 degrees Fahrenheit and watch the element as it heats up. The rod should be replaced if it does not begin to glow red. If your oven is out of warranty, don't let this repair scare you—replacing a heating element doesn't require you to be an electrician.