Ovens are basically very simple appliances designed to provide a baking chamber into which the temperature can ideally be controlled at any desired setting with minimum fluctuations in temperature level throughout the whole chamber unit, thus providing even cooking and baking.
Since they're used on regular basis and thus submitted to extreme heat conditions, it is normal for some of its components to become loose (sensor), to change values (sensor, elements, thermostat), to become shorted out, or otherwise defective as in no longer making contact (relays), or completely rendered inoperative after submitted to an unexpected power surge (Electronic Range Control or ERC).
1. A Burnt Oven Light
One of the most common problems encountered is a burnt light inside the oven, which most people can easily fix by removing the protective glass cover held in place with a specially formed spring wire that can easily be removed by sliding it over to one side and freeing the glass dome which is then removed to give access to the light bulb. Once removed, it needs to be replaced with the same type of “appliance light bulb.”
2. Control Panel Non-responsive or Blank
1) For ovens controlled from an electronic range control board (ERC) with a digital display, if the display is blank and none of the buttons work, it could be caused by a blown fuse or tripped breaker, but it could also likely be that your ERC has failed. You can locate the fuse and replace it, but if there is voltage present at the ERC power in terminals, you will likely need to replace the control board.
2) The control panel display changes when pressing the buttons, but it doesn’t operate properly while often emitting sharp beeps (but not always). This tells you that while some section of the ERC is still working, the control board has failed and the ERC needs to be replaced.
3) While the display is still on, if there is no change when you press any buttons, you can assume that the ERC failed at the keypad level and needs replacement.
3. Oven Not Heating Up
If you have a digital oven with an Electronic Range Control that is operating properly, or if your oven operates from an analog control, an oven that does not heat can be caused by one of several factors.
1) Both elements are burned-out (not likely but possible).
2) Loose, cut, or burnt wires.
3) A blown thermal fuse.
4) A defective temperature sensor.
5) A defective analog thermostat control.
The first thing to do is to check how the oven elements are behaving in relation to each other. When the selector switch is set on "Bake," the bottom element controlled by the thermostat should normally come on to start the warming process of the oven.
After a preset delay, an electrical relay will switch the power from the bottom element to the top element. If your oven is a convection type, the power will finally shift to the rear heater inside the oven (behind its back wall). Once this cycle is complete, the whole process starts all over and just keeps going to provide the evenest temperature throughout.
Note that some ovens might have a dual top element, with only one of them used for baking while the other one’s purpose is to add extra heat when broiling. If any one of the elements comes on, the problem is not that the oven does not heat at all, but rather that it produces insufficient heat or that it heats unevenly and burns the food (section 4).
The first thing to do is to unplug the appliance or shut off the circuit breaker at the main electric panel. You should then open up the appliance’s control panel to expose the electronics and trace the wiring back to the thermal fuse, which should read 0 ohms resistance on your multimeter.
Each of the heating elements can then be unscrewed from the oven box, one at a time, and pulled inside the oven box. Disconnecting one side of the elements, you can take a resistance reading across the terminals with your multimeter. If it shows infinite or extremely high resistance, it should be replaced.
If, however, you should get a resistance reading between 20 to 40Ω, you might want to remove the back panel of the appliance to expose the wiring and check for damaged or loose wires. Remember that for the oven not to heat at all, none of the elements are working.
The temperature sensor can then be checked with a resistance test—with one side disconnected, if your multimeter gets a reading of ∞ (infinity), it would indicate that the internal thermistor is “open” or burned-out and the temperature sensor needs to be replaced.
With everything tested and good at this point, it is time to question your analog control thermostat and replace it.
4. Oven Burning the Food (Or Uneven Baking)
As in section 3, start with testing the oven’s behavior while heating up. If the food burns at the bottom, it's likely that the top element doesn’t come on, or perhaps that the bottom element remains “ON” while the top one gets its cycle.
If the top of the dish burns, however, leaving the bottom uncooked, the same problem is now happening, but with the bottom element not coming on at all, or the top element staying “ON.”
1) One of the elements is burned-out (common cause).
2) Loose, cut, or burnt wire.
3) A defective relay switch or PC control Board.
Here again, you’ll need to unplug the appliance from its wall plug or turn off the circuit breaker before exposing the inside and all its electronics.
With that completed, do an overall inspection of the wiring leading to the defective element for burnt, cut, or loose wires or connections.
The next step is to remove the wire from one of the terminals of the defective element in order to isolate it (as described in section 3) and check the resistance reading across its terminals. The reading should be between 20 and 40Ω. If you get a higher reading or infinity, replace the element.
If, however, the element does have the proper resistance reading, you most likely have a defective control board or one of its relays and need to replace the board.
5. The Oven Doesn’t Heat to the Correct Temperature
You will notice a problem like this when your food comes out undercooked or overcooked (if not burnt) when it’s set at the prescribed temperature of your recipe. It used to be fine, but you now have to adjust the temperature setting or the cooking time. There are a couple of reasons that can cause this to happen, such as listed below.
1) The temperature sensor inside the oven changed its characteristic value.
2) The temperature sensor is somehow touching the oven wall, thus picking up the temperature of the wall instead of the surrounding air.
3) You have just acquired the appliance (new or used), and the oven doesn’t heat as the previous one did. The oven’s calibration could be off the proper temperature setting.
The first thing to do is to inspect the temperature sensor inside the oven cavity to make sure that it is well secured with its fastening screws and that the stem doesn’t touch anything inside the oven.
A temperature sensor provides a resistance reading to the control board to let the board know how hot to heat the oven. Its resistance value varies with the oven’s temperature.
The next step is then to verify the sensor’s resistance with an ohmmeter, which at room temperature should be between 1080 ohms and 1090 ohms. A resistance reading far off from that would indicate a faulty sensor and would need to be replaced.
The 3rd step would consist of calibrating the oven. For this step, however, you will need the user’s manual and follow the manufacturer’s instructions, as every appliance differs in its method to do this.
Before starting the calibration process, you can and should test the accuracy of the oven with an oven thermometer by preheating the oven at 350°F (177°C) and recording the temperature readings after 20 minutes and every 20 minutes for the next 90 minutes to two hours.
The sum of all those readings divided by the number of readings will provide you with the average overall temperature needed to establish the differential from the set 350°F (177°C). The temperature differential, either lower or higher, will be the number of degrees needed to recalibrate the oven to its proper setting.