Common microwave oven problems, common faults and how to fix them

Common microwave problems and faults and how to fix them

The microwave oven has to be one of the most popular household appliances ever devised. With its operating simplicity and speed of performance, it is an essential part of the modern kitchen. Owing to our dependence on such devices, it becomes necessary to learn the basic skills required to tackle common microwave problems.

However, troubleshooting microwave faults must be performed with the greatest care and safety. These ovens probably represent the most lethal appliances in your kitchen today. Handling them without adequate care and safety could have fatal consequences. During periods of operation the microwave utilizes extremely high voltages (5000 V). If you are attempting to remedy any microwave problems, it is essential to realize that this appliance possesses a high voltage capacitor that will stay charged even after the microwave oven has been switched off. Before trying to fix any microwave faults the capacitor must be discharged.

Dismantling the metal cover around the microwave oven can leave you exposed to dangerous electrical connections. Never run the microwave without the cover as there is the potential of irradiation, and you can be exposed to harmful emissions if the waveguide is damaged.

Always take the maximum precautions while working on your microwave. If you are inexperienced in working with such devices, it might be safer to seek the services of a trained service technician.

There are various types of problems that can affect a microwave oven, and analyzing some of these issues can help you troubleshoot these machines

Microwave is dead

If the microwave appears dead, this could indicate a problem with the Line Fuse, which will blow if excess current is being used by the microwave components. While this fuse is easily replaceable, there may be other issues that are causing the appliance to over-draw power. There might also be a problem within the High voltage circuit of the microwave, in particular with components such as the diode, magnetron, high voltage capacitor, or transformer. Other factors that may cause this condition include a blown thermal fuse that should be tested for continuity or Thermoprotector that has tripped. (This is a small component that ensures that the microwave does not overheat.) Certain microwave models may require the system clock to be set before they commence functioning.

Microwave Does Not Heat

Most microwave ovens will include a high voltage diode that is responsible for converting the A/C power output delivered by the transformer to D/C. During this process the voltage reaches its peak capacity of 5000 volts. This generates enough power so that the magnetron is able to provide the cooking energy within the oven. A failure in the diode will result in a lower A/C voltage reaching the magnetron, which may not be sufficient. Diode failure is often accompanied by visible signs of a burn out. If the diode appears to be unaffected, it may be tested with the aid of a volt-Ohm meter that has the capacity for handling diodes.

Most microwave ovens are usually equipped with 3 door switches. A failure with any one of these switches can result in the microwave oven not switching on and consequently no heat is produced. These switches should be checked for continuity with an Ohm meter.

The microwave oven is essentially powered by the Magnetron tube that utilizes a high D/C to generate the waves that are responsible for cooking food. Any damage to the magnetron will prevent the device from heating up. If the microwave oven has been run while empty, this could have burned out the magnetron. This part cannot be repaired and will need to be replaced.

A defective high voltage capacitor may also be responsible for the oven's failure to heat up. Any problem to the HV capacitor will affect the functioning of the complete high voltage circuit. The HV capacitor may be tested only with a specialized VOM meter that has capacitance testing ability. Even when switched off, the HV capacitor may retain a charge of about 3000 volts. Therefore, it is always advisable to leave its testing to an authorized service technician.

There might also be issues with the Thermoprotector, Thermal fuse, or High Voltage Transformer that can lead to this type of problem.

The Microwave Runs Briefly and then Stops


In most cases, this problem is caused by a defective door switch that fails intermittently. These switches should be inspected for any signs of arcing, overheating, or burning. They must also be checked for continuity. Switches that display any visible signs of damage or that display intermittent continuity should be replaced. This type of problem could also be indicative of an intermittent short on the High Voltage Transformer. A tripped thermoprotector or defective thermostat may also result in the microwave running intermittently.

Apart from these issues, this problem might be a sign that certain components within the Touchpad, control Panel, or Main Control Board have been damaged.

The Microwave Light Bulb is not working

The microwave light bulb is usually quite easy to replace. Simply reach in and replace the bulb. If this does not work, it would indicate a problem such as the light bulb socket burning out or some type of wiring defect.

The Microwave Turntable Does Not Turn

In most cases, lack of movement in the turntable is a sign that the turntable motor has been worn out or has burned out. This type of problem can occur fairly often and this part is easily replaced. However, if the motor is still functional this could indicate a defect within the main control board or User Control and Display Board. If the microwave oven has a button on the touchpad responsible for switching the turntable on and off, then this could indicate a problem with the Touchpad and control Panel.

The Microwave Buttons Do Not Seem to Work

In most cases, lack of response from the microwave buttons would indicate that the touchpad or the control panel are defective or have been damaged. (Excessive cleaning of the touchpad can cause this.) Certain microwave models require that the door be shut before the touchpad is activated. Another issue with machines like this is that they tend to go into 'sleep' mode quickly. Simply opening and closing the door once should be enough to re-activate the oven. A 'confused' controller may also be responsible for this type of situation. You can unplug the device for 1-2 minutes to let it reset.

The Microwave Display does not function

Usually this type of problem is related to the functioning of the microwave Display Board. A complete failure in the display would indicate a problem with the main board or display board. However, if part of the display is available, there is clearly a malfunction in the display board. You might also be dealing with a display panel that is physically broken and will need to be replaced. Sometimes, this type of problem may be resolved by resetting the microwave. (Switching off for 1-2 minutes)

The Microwave Starts by itself

This type of problem usually indicates a faulty triac or relay, or could point to a problem with the controller. You can try resetting the machine to see if the situation corrects itself. If this does not work, it could indicate problems with the power supply or defects in the touchpad.

The Microwave is Arcing (Sparking)

If sparks are produced in the microwave oven at the time of operation, this could indicate that the Waveguide Cover is defective or has shorted out. You may remove this cover to check if this solves the problem. Sparking can cause damage to the microwave cavity and any damaged areas should be repaired. The waveguide cover will have to be replaced if any of the underlying connectors are burnt out or have melted.

If there is sparking along the side walls of the microwave oven, this could indicate that the paint along the side walls has been chipped. This type of problem can be fixed by covering up any exposed metal spots in the oven with a microwave safe paint. This type of sparking may also be seen near rack supports, where the paint has worn away leaving exposed bare metal within the oven.

In general, any exposed metallic edges or carbonized food residue within the oven cavity can cause arcing.

The Microwave Door does not open

If the oven door is stuck and does not open, there is every possibility that the Open Lever has broken, and will need to be replaced. There might also be an issue with the Door Spring located within the door. This spring is responsible for exerting a downward force to the door hook.


This type of problem might also indicate the presence of a broken door latch. This latch is mounted on the inside surface of the oven, and engages with the door hook to ensure the oven door remains closed when it is switched on. A broken door latch or actuator will prevent the door from being opened.


In addition, problems with the Door Hook, Button, Button Spring or the Handle Actuator might stop the door from opening.


Disclaimer: The information provided has been prepared as a guide only and the steps taken are likely to vary for different appliance models. We strongly recommend using a qualified engineer to undertake major repairs and fault finding.



    26 Apr 2017 by steve

    • My 3 year old Panasonic top-of-the-range microwave failed gradually. We have used it a lot on a daily basis. It took longer and longer to heat up food or liquids. I discovered that it would heat a cupful of liquid to boiling point reasonably quickly, but not a pint of liquid. That would only become lukewarm. Eventually it ceased working entirely, so no internal light, no display, nowt!
      Is this magnetron? Capacitor? Diode? which is most likely to be faulty.

      29 Feb 2020 by David

      • The Beeper on M/Wave does'nt work when time is up, can I fix it.

        28 Jun 2021 by Robert

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