You can be using your range for cooking and baking for years always with great results, until this one day when your oven starts taking longer to bake and seems to cook the top more than the bottom or vice versa.
As the problem gradually worsens, you realize that something is not quite right with your oven and that you have to either call in the technician or give it a look and appraise on your own for obvious problems and maybe fix it.
Before rolling up your sleeves and getting dirty, you should however realize that you should get yourself familiar with the way things are working down in there so that you know what to search or look for.
What you have to consider now is that several heating elements are used to operate the oven for an even temperature to circulate around the food and cook it all around. The main heater element for baking is the bottom one, standing about 1 inch above the bottom of the cavity.
It is the first one to get activated followed by a top element hanging from the ceiling of the oven box that goes on next. You should note that the top of the oven cavity can have to two elements, one of which is strictly for broiling, or if it only has one, it is used both for baking—at a controlled temperature and when broiling—at about 500 to 550°F (260 – 290°C).
For those who have a convection oven, there is also another element inside the back wall of the oven just about in the center of the wall and equipped with a fan that blows that additional heat in and serving as well as a circulating fan pushing the heat around the oven cavity to make the temperature even throughout the box.
An initial visual check of the bottom and the top elements should be the first step in troubleshooting such a problem and is simple enough to do, by turning the oven on for baking while watching for the bottom and top elements to glow.
Electric Oven Element Not Glowing
If one or the other element doesn’t come on, the side exposed to that element would be less cooked or uncooked with the opposite surface exposed to a glowing element would get overcooked.
If it’s simply that one of the elements doesn’t glow quite so brightly or is only warm to the touch—be extremely careful not to feel by touch—it might’ve changed in resistance value but still radiating enough heat to inflict a bad burn.
While doing this visual test, check to see if the fan in the back of the oven is working as this would also affect the proper operation of the oven. Follow steps 1.1 to 1.9 to determine if the problem lies with one or both of the elements.
Temperature Sensing Probe
The temperature probe is the component protruding from the back wall of the oven cavity a few inches long and is simply a thermistor, with varying resistance values depending on the temperature it is submitted to. This variable resistor works directly in coordination with:
A) the thermostat control onto which it is attached in analog-controlled appliances.
B) the EOC board where the leads are plugged into the digitally controlled units processing the resistance readings to control the oven temperature. Step 2.1 shows how to test the probe on digital units.
Before taking anything apart, do a physical check of the probe making sure that it is properly secured to the oven wall and not touching anything else in its surroundings.
Convection Rear Element
If your oven just seems to take longer to bake or if the baking is uneven throughout the oven cavity, there may be a possibility for the convection element to be defective.
This possibility, however, can only be confirmed with a resistance test applied to that element, and it can only be done by removing the back cover or panel from the range and the element cavity’s protective cover. The rear element can be checked by following steps 1.6 to 1.9.
If your oven doesn’t heat at all or the digital readout doesn’t light up, you could be dealing with a defective thermal cutout.
The thermal cutout switch or thermal switch is a special safety device installed at the back of the oven cavity near the top elements. It is designed to remove the power from the heating elements and shut down the oven to prevent it from catching fire in cases where the oven would overheat.
The thermal cutout can be accessed by removing the back panel from the appliance. You should easily see the two wires leading to the thermal cutout’s terminals. The thermal cutout is secured right next to the top element terminals. Step 2.2 will show you how to test it.
Oven Thermostat Control (Analog)
The mechanically activated oven thermostats conveniently located on the front panel were the first type of temperature controls in ranges and ovens and are still found in use today.
They usually work in conjunction with the temperature probe which is physically connected to the thermostat control to control the temperature level at which to cuts off the power. It also contains an adjustment screw to calibrate the oven (when needing it) if it goes off by a few degrees.
Electric Oven Control (EOC) Board
The EOC board is the central control system of your digital oven. All controls and sensors affecting the functions of your oven are connected to the EOC board where the information in the form of electrical signals activates whatever elements, timer, or other functions the keypad is set at.
The keypad is usually an integral part of the EOC board.
1. Checking the Heating Elements
Step 1.1) The first step in troubleshooting is the visual test as described for each component listed above.
Step 1.2) With this done, turn every control off on the appliance and unplug it from the wall or switch the breaker off at the main circuit breaker panel.
Step 1.3) Open the oven door and unscrew one of the elements from the oven box and pull it inside the box. Removing the door completely will make access to the inside of the box even easier.
Step 1.4) Disconnect one side of the element (to prevent an erratic measurement from the rest of the circuitry) and take a resistance measurement with your multimeter across the element’s terminal.
The reading should be around 20Ω to 40 Ω. At 0Ω you know that the element is shorted and with a larger reading that its value has changed, while an open or ∞ (infinity) reading indicates a blown element—any of these 3 cases requiring the replacement of the element.
Step 1.5) With a good reading, replace the element and secure it in place then do the same procedure with the second element.
Step 1.6) With both elements testing OK, pull out the appliance from the wall or from its opening in the wall (for wall oven) and place it at a stable position while providing access to the back of it.
Step 1.7) Remove the back panel(s) to expose the internal wiring and components. Be careful when moving the back cover over as there might be some wires still attached to it, but they should provide enough slack that you shouldn’t have to remove them.
Step 1.8) Do a visual inspection of the components and obvious loose, burnt, or otherwise damaged wires.
Step 1.9) With the terminals of the circular convection heater exposed, disconnect one wire from its terminal and repeat step 1.4 and check its value.
Note 1 - Remember at this stage that if the oven doesn’t heat at all, none of the elements is getting any voltage.
2. Checking the Other Components
Step 2.1) If your control panel is digital, you can check your oven temperature sensor next, since it is plugged into the EOC board instead of being built into a thermostat control.
Looking at the EOC board, unplug the temperature sensor from its connector on the board and use your multimeter to measure the resistance across its two prongs.
At room temperature, the reading should be around 1080Ω. There is a slight possibility that your sensor goes bad at a higher temperature, but it is not likely, and if it’s good at room temperature, the fault is usually with the EOC board.
Step 2.2) The next check should be to verify the status of the thermal cutout which is located close to the top element. By unplugging one of the 2 wires leading to it, you can measure for continuity across the terminals, which, if there is continuity, the cutout device is operational, and if it checks open, it should be replaced.
Step 2.3) With an oven-controlled with an analog thermostat, if the temperature probe, the thermal cutout, and the elements are all testing OK, you’re next step will be to replace the thermostat control, as this component can only be tested with the power on, making the process more hazardous. With a digital EOC, the board should be replaced.
Note 2 - While working at or in proximity to the EOC board, you should get and use an anti-static wrist strap to ground yourself to the appliance’s chassis. This will prevent you from inadvertently discharging static electricity into some component on the PC board and “frying” it.
Note 3 - If you test the oven temperature with a thermostat and get a variance in temperature from your set temperature no less than 35°F (19°C) lower. you could simply need to re-calibrate your appliance. You can consult your owner’s manual for the proper procedure.
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