How to Troubleshoot a Microwave/Oven Combo?

An oven combined with a microwave is a fantastic tool, both for thorough cooking and for reheating leftovers! However, such a useful piece of equipment naturally comes with its own set of malfunctions. You may find yourself wondering how to troubleshoot an oven/microwave combo.

In this article, we will give you our complete list of the 13 most common issues with oven/microwave combos and the possible reasons for those issues so you can troubleshoot the problem! This list can be found below:

1. Microwave Not Heating

The possible reasons behind your microwave refusing to heat up are listed below:

• Diode – The diode in a microwave is located near the magnetron. It’s responsible for powering the magnetron which heats the microwave. After disconnecting power and discharging the capacitor, check to be sure that the polarity is low on one end of a resistance meter and high on the other. If not, you will have to replace the diode.
• Door Switch – The door or interlock switch is responsible for powering up the microwave as soon as it senses that the door is closed for safety. They are inside the cabinet of the microwave and are marked “C” and “NO.” Using a multi-meter, check them for continuity. If there is no continuity, replace the switches. 
• Magnetron – If the magnetron cannot provide power to the microwave, the microwave won’t heat. Remove the cabinet, disconnect from power, and discharge the high voltage capacitor before disconnecting wires from the magnetron. Then use a multi-meter to check continuity between 2-3 OHMs. Replace a faulty magnetron.
• High Voltage Capacitor – A burnt out high voltage capacitor will result in the failure of the whole voltage circuit and no heat in your microwave. Use a VOM meter to check that the capacitor is working properly after disconnecting from power and discharging. Only a licensed professional should handle the replacing of a capacitor.
• High Voltage Transformer – The high voltage transformer is a part of the voltage circuit and can sometimes overheat, causing a smell of something burning and stopping your microwave from heating up. If you do smell burning and your microwave won’t heat up, get help from a professional to check on and replace the high voltage transformer.
• Thermal Fuse – The thermal fuse is meant to shut down power in a microwave if it overheats. If it has blown, a multimeter will show it’s lack of continuity, and it will need to be replaced. Note: thermal fuses cannot be reset, and should only be replaced by professionals due to their involvement with dangerous amounts of electricity!
• Thermoprotector – A thermoprotector cuts off an overheating microwave’s power. Test the thermoprotector for continuity using a multimeter, then rely on a licensed professional to reset or replace the thermoprotector.
• Main Control Board – The main control board may become defective, but it is not often the case. All other causes should be examined before moving on to replacing the main control board, and even then, only a professional should be allowed to accomplish the task for safety reasons.

2. Microwave Not Working

If your Microwave is completely unresponsive and will not work at all, check the things on the following list:

• Line Fuse – If the line fuse has blown, the microwave will not work. High amounts of dangerous electricity are involved in a line fuse and therefore they should only be replaced by a professional.
• Main Control Board –  See Problem No. 1., “Main Control Board,” to troubleshoot this issue.
• Thermal Fuse – See Problem No. 1., “Thermal Fuse,” to troubleshoot this issue.
• Thermoprotector – See Problem No. 1, “Thermoprotector,” to troubleshoot this issue.

3. Microwave Light Bulb Not Working

One of the simpler issues your Microwave might present you with is a light bulb that just won’t turn on. This could be the result of the following:

• Light Bulb – You may simply need to change the light bulb in your microwave. For safety reasons, make sure the microwave is completely turned off when removing the light bulb, and always be sure to replace the bulb with the correct model.
• Main Control Board – See Problem No. 1, “Main Control Board,” to troubleshoot this issue.
• Light Socket – If the bulb of the microwave is not blown and a new bulb will not light, check and replace the light socket which the light bulb is placed in.

4. Microwave Shuts Off After a Few Seconds

If you’ve found that your microwave starts up fine, then shuts shown after only a few seconds of operation, it is likely the fault of one of the following problems:

• Door Switch – See Problem No. 1, “Door Switch,” to troubleshoot this issue.
• Main Control Board – See Problem No. 1, “Main Control Board,” to troubleshoot this issue.
• Touchpad – The touchpad is not touch-sensetive, but uses a type of membrane to synthesize touch sensitivity. Replace a faulty touchpad by looking up the corresponding membrane for your microwave model and ordering it to be replaced.
• High Voltage Transformer – See Problem No. 1, “High Voltage Transformer,” to troubleshoot this issue.
• Thermoprotector – See Problem No. 1, “Thermoprotector,” to troubleshoot this issue.
• Thermostat – The thermostat is responsible for cutting off the electric power on the outside of the microwave if the magnetron is too high for safety. If it is operating correctly, it will shut your microwave down after a few moments of overheating.

5. Microwave Turntable Not Turning

If you have noticed that the turntable responsible for rotating your food dishes inside the microwave is not turning, or is moving irregularly, check the list below for the reasons:

• Turntable Motor – The turntable motor is located under the bottom panel of the microwave. Detach it from power and replace the motor if it has malfunctioned.
• Glass Tray Drive Coupling – The glass tray drive coupling may be broken or stripped, and should be pulled off of the drive motor shaft carefully and inspected before being ordered for replacement.
• Glass Tray Support – The glass tray support can break and strip just as easily as the coupling and should be pulled out and replaced if any tears or breaks are discovered.

6. User Control and Display Board

There are few things more frustrating than an uncontrollable microwave due to an unresponsive display board. Check the reasons for this issue below:

• Touchpad and Control Panel – For Touchpad issues, see Problem No. 4, “Touchpad.” For Control Panel problems, you will notice that the buttons may only work inconsistently. This will mean that the entire control panel must be replaced.
• Main Control Board – See Problem No. 1, “Main Control board,” to troubleshoot this issue.

7. Microwave Turns on By Itself

If your microwave is turning on by itself, there is usually only one reason for it, and that has to do with the Main Control Board. If it truly is the Main Control Board that is at fault, see Problem No. 1., “Main Control Board,” to troubleshoot this issue.

8. Microwave is Sparking or Arcing

A sparking or arcing microwave can be unsettling. To understand this issue, check out the list below:

• Waveguide Cover – The waveguide cover is responsible for protecting the hardware of the microwave from food particles or debris. If it is damaged, the microwave can begin to spark or arc dangerously and should not be operated. Order the correct model of waveguide cover and replace the entire thing if any damage is discovered.
• Inside Paint and Rack Support – If the metal inside your microwave, either on the rack or in the chamber, is exposed due to chipping paint or plastic, it can cause your microwave to interact with the metal and create sparks. You will need to replace any scratched or damaged racks.

9. Microwave is Loud or Noisy

Microwaves naturally emit some noise, but if you find an irregular amount of noise coming from your device, browse the list below for possible reasons:

• Magnetron – See Problem No. 1, “Magnetron,” to troubleshoot this issue.
• Exhaust Fan Motor – A microwave’s exhaust fan motor may be damaged or slow, causing the exhaust fan to spin irregularly or create too much noise. If this is the case, the exhaust fan motor should be replaced entirely after being disconnected from power and discharged safely.
• Stirrer Motor – The stirrer motor is responsible for dispersing the microwaves used to heat the food in the chamber of a microwave. If it is damaged, it can cause a loud humming sound and should be replaced by a professional.
• Turntable Motor – The turntable motor’s defects could cause it to make more noise than it should. See Problem No. 5. “Turntable Motor,” to troubleshoot this issue.

10. Microwave Display Not Working

Your microwave won’t be much help to you if you cannot read the display of timer numbers and see what you are setting your food to cook to. Therefore, it can be helpful to understand the issues on the list below:

• Microwave Buttons Not Working – The problem may not be your actual display, but instead, an issue with your microwave’s user interface buttons. The display cannot show anything if it is not receiving any input from the buttons. Check section 6. Of this article for more information on broken microwave buttons.
• Display Board – A display board is the power that is sent to the display of the microwave. If only part of the microwave display is visible, the display board is damaged and must be replaced.
• Main Control Board – See Problem No. 1, “Main Control Board,” to troubleshoot this issue.

11. Oven Won’t Heat, Turn On or Off!

If your oven is entirely unresponsive and will not even turn on, or worse, turn off after being turned on, you should understand the possible reasons listed below:

• Bake Element – The bake element of your oven is responsible for heating the oven up. It can often be uninstalled and replaced easily as long as you find the correct model and disconnect electricity from an electric oven.
• Igniter – A gas oven needs the igniter to ignite the gas that engages the cooking process in an oven. If it is broken, it will take longer than a minute to ignite and should be replaced.
• Broil Spark Electrode – Similarly to an igniter, the broil spark electrode lights the gas in a broiling gas oven. If it is cracked or takes longer than a minute to ignite gas, it should be checked for correct polarities and connection to the wall outlet. If these things are intact and normal, it will need to be replaced.
• Broil Element – The broil element is normally a red color when heated and glowing. If it does not turn red and glow, it is likely burnt out and will display blisters or holes. Test the broil element with a multimeter for continuity, then replace it with the corresponding broil element model.
• Incoming Power Problem – It may be that your oven is not receiving power. Carefully pull the oven away from the wall and inspect the wall outlet and power connections for malfunctions. 
• Thermal Fuse – Like the same component in a microwave, the thermal fuse is responsible for turning off the oven when it overheats. If it is tripped after an overheating experience, it can sometimes be reset; however, a damaged thermal fuse will have to be replaced.
• Loose or Burnt Wire Connection – Loose or burnt wires can not only cause damage to your oven, but they can be dangerous. Carefully disconnect the oven from a power source if these are discovered. Any burnt wires should be replaced and handled by a professional electrician.

12. Oven Control Board

Just like with a microwave or any computing device, your oven won’t be much good to you if the control board does not work. Check out the list of possible reasons for this issue below:

• Safety Valve – The safety valve on an oven prevents uncontrolled lighting in gas ovens. Safety valves are necessary pieces of equipment for your safety, but should be replaced by professionals if damaged.
• Temperature Control Thermostat – After unplugging the oven from the wall and locating the thermostat behind the back panel, check the temperature control thermostat of your oven by using a multimeter. If you receive no reading or a reading far from zero, it must be replaced.
• Valve and Pressure Regulator – Use a manometer to test the gas oven’s valve and pressure regulator. If it is not displaying continuity between 1 and 1.5 OHMS, it mut be replaced. 

13. Oven Temperature Not Accurate

The oven temperature must be accurate, or else you will find yourself with many ruined meal plans! In order to understand this problem, check out the list of possible reasons below:

• Temperature Sensor – A thermostat sensor can be worn down and cause your oven to overheat despite the heat settings you determine. It must be monitored for inconsistency before being replaced if faulty.
• Convection Element – If a convection oven circulates cool air, shut off the power to the oven, remove the oven door and remove the panel covering the heating coil. The heating coil may display burns or bubbles and should be tested with a multimeter for continuity before resorting to replacement.
• Convection Motor – After turning off the power and removing the top panel covering the convection motor’s fan, be sure that the fan itself is not dirty or obstructed. Then, test the moto with a multimeter and replace it if it shows a lack of continuity.