Two complaints arrive as the same sentence. In the first the oven never gets hot. In the second it heats but the results are wrong: cakes sinking, one side browning faster, or a roast taking half as long again as it used to. They deserve different checks.
Nothing Heats At All
On an electric oven, check the breaker. Ranges usually sit on a double breaker, and losing one leg can leave the surface elements or the clock alive while the oven stays cold. Switch it fully off and on again. If it trips again, leave it off and have it looked at.
On a gas oven, check other gas appliances in the house work, and that the supply valve behind the range is open. If you can smell gas, do not test anything: leave the house and call the gas emergency number from outside.
Also check the oven is not in a delay start, sabbath or demo mode, and that the door closes fully, since a door that does not latch properly can stop a heat cycle.
It Heats, but Badly
Buy an oven thermometer, hang it in the centre, set 350°F and leave it for twenty minutes after the preheat tone. Then read it, and read it again ten minutes later. What you learn:
- Consistently 25 to 50°F off: a calibration offset, which many models let you adjust in the settings. The manual gives the sequence.
- Swinging widely: points at the temperature sensor or the control rather than calibration.
- One side browning faster: often a convection fan issue, a damaged element or an oven that is not level.
- Everything slow but even: a weak element, or on gas an igniter that has aged and no longer opens the valve promptly.
Two habits distort results before any of this: crowding the oven so air cannot circulate, and opening the door repeatedly during baking. Rule those out first.
Elements, igniters, sensors and control boards sit behind panels carrying mains voltage or next to a gas connection, so when calibration does not explain it, book a Maytag oven repair and bring your thermometer readings.