5 Reasons Microwave Keeps Blowing a Fuse | How To Fix It

Microwaves have fused to ensure safety when in operation. In fact, this is true for any electrical appliance. Fuses blow whenever there are any unsafe conditions. For instance, a microwave relies on a thermal fuse to blow to prevent overheating.

But what happens if your microwave keeps blowing a fuse whenever you start it? In this case, there might be several causes of the problem. In this article, I’m going to talk about some of the main reasons your microwave is blowing a fuse.

5 Reasons Your Microwave Keeps Blowing a Fuse

There are several reasons your microwave will blow a fuse, so to help you work your way through the process of troubleshooting, I have listed each possible cause below in order of the likelihood they triggered the fuse to blow. So start with number 1 ‘Problem with Power Outlet’ and work your way down the list in order.

1. Problem With Power Outlet

Before you begin inspecting your microwave for faulty components, you should first check whether any external issues are causing the fuse in your microwave to blow. Start by checking whether the power outlet the appliance is plugged into is faulty. If the plug or the wall outlet shows any signs of scorching, you’ll have to replace the outlet.

2. Water Ingress

It’s not uncommon to find a puddle of water on the floor of your microwave oven. The likelihood of this happening is increased significantly when you prepare high-moisture food. Water in an electrical appliance is bad news and can lead to a blown fuse.

Whenever you notice water in your microwave, you should wipe it off immediately. To avoid your microwave getting wet, you should always cover food containers when heating them. You should also make a habit of wiping off traces of condensed water in the appliance.

3. Faulty Interlock Door Switch

Did you notice that the fuse in your microwave blows when you open the door of the appliance? If so, there is probably an issue with the interlock door switch in your microwave. The door switch is an important component that keeps you safe by ensuring microwave radiation doesn’t leak out of the appliance and cause burns on your skin.

The door switch ensures that the appliance will emit microwave radiation only when the door is closed. But when the switch stops working properly, the fuse has to blow to ensure you are protected from microwave energy.

4. Defective Magnetron

The magnetron is the core component of a microwave oven. It generates microwaves that heat your food quickly. Like any other component in your microwave, the magnetron can become defective over time.

You can test whether this component is faulty or not with a multimeter. Simply set the ohm setting on the multimeter and connect its leads with the terminals of the magnetron. You should see somewhere between 2 to 3 ohms of resistance. In case you don’t, the magnetron is defective.

5. High-Voltage Capacitor Failure

The high-voltage capacitor stores and releases electricity to the magnetron. In case the fuse blows as soon as you start your microwave, it could be due to a faulty capacitor. Replacing or even testing the high-voltage capacitor is not an easy task and should be left to the professionals if you don’t have a lot of experience fixing appliances.

Safety Warning

One thing that you should know is that certain components of the microwave, like the high-voltage capacitor, can cause serious injury even if you’ve unplugged your microwave. This can happen due to the capacitor storing a potentially lethal amount of electricity. That’s why you should be cautious when inspecting your microwave.

Some of the rules you should remember are to wear insulated gloves, remove any jewelry or watches, and avoid touching metal components unless you know your way around appliances.

How to Test and Replace a Blown Fuse

The process of testing and replacing a fuse in your microwave is pretty straightforward. You can do it at home as long as you follow the safety precautions mentioned above. Here’s a short guide on how to test and replace a fuse:

  1. The first thing you’ll need to do is unplug your microwave.
  2. Wait for at least 15 minutes to allow components to discharge.
  3. Remove the microwave frame to access the fuse you want to test and replace.
  4. Unclip or unscrew the fuse and take it out of your microwave.
  5. Grab a multimeter and set it to the ohm setting.
  6. Connect the leads of your multimeter to the fuse.
  7. In case the reading on your multimeter shows infinity, you’ll need to replace the fuse. If the reading is close to 0 ohms, the fuse is not blown.
  8. If you have to replace the fuse, simply put the replacement in the same position the original was in and reassemble the microwave.

In case you want a more detailed guide on how to replace a microwave fuse, you should watch the video below.

Replace Your Microwave Fuse

Which Fuse?

There are multiple fuses in a microwave. Your microwave contains a main fuse, which is tasked with preventing the flow of electricity in the event that too much current passes through it. You can easily recognize this type of fuse due to its rectangular shape. This component is two inches in length.

There is also a thermal fuse in your microwave that will stop the appliance from overheating in unsafe conditions. The thermal fuse is very important because it can stop a potential fire. The thermal fuse is larger than the main fuse and looks like a black cylinder.

What you should remember when you’re ordering replacement fuses is that they should have the same amp rating as the original.

Cost of Repair or Replacing Microwave

Replacing a fuse is a cheap and easy fix that you can do at home. However, you might need to replace other components if your microwave keeps blowing a fuse. Some of the components that can cause an issue like this include the high-voltage capacitor and the magnetron.

There are safety concerns when it comes to replacing a high-voltage capacitor, so you’ll probably need to hire a professional repair technician to replace the component. In case you need to replace this component, you might want to consider buying a new microwave.

Appliance Service Technician | Website | + posts

Andy has over 8 years of experience working on residential household appliances, performing diagnostics, and repairs across most major brands. He graduated from the Denver Institute of Technology, is NASTeC certified, and has worked for Mr. Appliance. Andy has contributed to features on major publications including Better Home & Gardens, Family Handyman, and Yahoo.com.