9 reasons your microwave keeps tripping the circuit breaker

Written by Adam Morris
5 Min read
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Table of contents

Picture the scene; you’ve just arrived home after a long and tiring day at work. You’re starving, the kids are nagging you for dinner and you’ve promised a friend you’ll meet them at the gym that evening.

Luckily, you’ve stocked the freezer up with some TV dinners, but as you pop one onto the microwave, close the door and click the start button, the circuit breaker trips leaving your microwave out of action. You wearily reset the circuit breaker and try again only for the same thing to happen.

Frustrating, isn’t it?

The reason this is happening is that the circuit can only handle a certain number of amps and for some reason your microwave is exceeding this limit, causing the breaker to trip.

Here are nine possible reasons why this is happening:

You’ve overloaded the electrical supply

Microwaves pull an awful lot of electricity from the circuit and can easily trip the circuit if that electrical load increases for any reason.

One obvious cause for a trip is that the microwave is having to share the circuit with other appliances – microwaves use around 12 amps of electricity and in an ideal world will have their own dedicated 20-amp circuit – if yours is having to share a circuit with other appliances, try moving the other appliance to a different position in the kitchen.

A malfunctioning microwave will also cause a trip in the circuit breaker, and you should carry out some further investigations to identify what the problem could be. You can test this by moving the microwave and plugging it into an area that is set to handle a higher amp rating. If it blows this circuit, then that’s a pretty clear sign that you have an issue.

The timer is jammed

Whilst older models of microwave feature mechanical timers whereas newer ones are electric, and when the electrical components wear over time or sustain damage it could cause the circuit breaker to trip.

Try resetting the timer by unplugging the unit and waiting for at least five minutes before plugging it in again. If this doesn’t work, you may need to consult with a certified technician for advice.

The interference suppressor has blown

Your microwave is fitted with a suppressor that helps to filter out loud noises that run through the appliance. It also helps to control the voltage, reducing interference to the control board and preventing electrical malfunctions.

If when your microwave trips it is accompanied by a loud noise, this is a sign your interference suppressor has blown.

The magnetron has an electrical leak

Microwaves use a device called a magnetron to generate electromagnetic waves. These waves vibrate water molecules to heat up food.

A failing or leaking magnetron could cause all kinds of issues with other electrical gadgets and appliances and could potentially be the main reason for your circuit breaker tripping.

The high voltage diode is short-circuiting

Defective diodes are usually accompanied by an electrical burning smell or loud humming noise. It is possible to replace a faulty or damaged diode, but if you are in anyway unsure it is always best to consult a specialist technician for advice.

The turntable motor is wet

The turntable in your microwave (the glass circular plate you place your food on) is undoubtedly one of the most important elements of the whole process. It should be regularly cleaned and maintained to ensure problem-free cooking as any dirt, debris or water could mean you run into issues.

The turntable motor is located just under the plate and is what rotates it during cooking. When something boils over or spills and isn’t cleaned immediately afterward, the liquid can travel down to the motor and short it, causing the circuit breaker to trip.

Rectifying a wet turntable motor unfortunately isn’t as easy as mopping up the water, the motor should be removed and tested with a multimeter before being tested again.

The door interlock switch has broken

If the circuit breaker is tripping when you open the door of your microwave, this could mean that the door’s interlock switch has been damaged or broken.

The interlock switches control an electrical cycle to ensure the microwave only operates once the door has been closed. Whilst these switches are usually very reliable, over time the door latch can sustain wear and tear and may not be making contact with the interlock sensor fully.

There is a faulty high voltage capacitor/diode

The high voltage capacitor and diode work together to double the voltage of the appliance. This provides the required amount of power to fire up the magnetron and cook the food inside.

Any issues with the voltage capacitor or diode will affect the smooth functioning of the complete high voltage circuit and eventually completely stop the circuit from working.

And finally, have you checked the fuse?

Have you considered the fact that the problem might not be related to the internal workings of your microwave at all?

Microwaves feature several different fuses that are designed to keep you and your home safe – door fuses will blow if the door hasn’t been closed properly, thermal fuses will blow if the microwave overheats, and the main fuse will blow if the high voltage capacitor has shorted.

How to replace a blown microwave fuse

  • Disconnect the microwave from the power socket
  • Remove the relevant access panel (check your manufacturer guide for details of how to locate this)
  • Unscrew or unclip the fuse and remove it
  • Replace the fuse with one that exactly matches the fuse you have removed
  • Reassemble the microwave and restore the power

A final word of warning

Microwaves have the potential to be much more dangerous than your other kitchen appliances. It will produce and store a lethal amount of electricity, which is still evident even if it has been out of use for several weeks.

Whilst replacement microwave parts are relatively inexpensive to purchase unless you are extremely confident and experienced with electrical appliances it may be safer to replace the microwave if you suspect serious electrical issues.

FAQs

Where is my microwave fuse located?

Microwaves actually have several fuses in different locations that are designed to keep you and your family safe, including the top, side, and behind the vent grill.
Your appliance manual will contain more detailed information relating to your specific microwave model, and these can usually be found online if you cannot locate the paper copy.

Can I plug my microwave into a regular outlet?

The safest way to operate a microwave is to plug it into its own dedicated circuit.  Microwaves require a lot of power and outlets being used by other appliances have the potential to interfere with the smooth operation of the oven.
Ideally, this outlet should be a 120 volt, individual, and properly grounded circuit.

How long should a microwave last?

Whilst larger families may find themselves having to invest in a new microwave every four to five years, the average microwave with normal use will last for around seven years.

Does a microwave have a reset button?

How to reset a microwave:
·       Find the cancel button and press it until it beeps and cancels all other operations
·       Press and hold the cancel button for 3 seconds

If this doesn’t work, unplug your microwave and leave it for 20-30 minutes before plugging it back in again.

Appliances made simple. 

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