What Are The Symptoms of a Bad Microwave Diode? (Answered!)

A microwave diode is one of the most important components in the appliance. Without it, it’s impossible to generate the heat required to heat foods and drinks placed in the oven cavity. Unfortunately, the component can go bad, so it’s important to understand the symptoms of a bad microwave diode. 

Generally, the symptoms of a bad microwave diode include sparking, buzzing and humming, and the appliance failing to heat. Running a continuity test helps to determine whether the diode has a problem. Getting a new diode for replacement is the solution if the current one fail the continuity test.

What Does a Diode Do in a Microwave?

The work of a microwave diode is to convert alternating current (AC) to direct current (DC). The conversion doubles the voltage to about 1,500 volts.

microwave high voltage diode

This high voltage is used to power the magnetron.

Once this high-voltage power reaches the magnetron, it is converted to radiation heat, which cooks your food or drink.

The diode will also protect high-voltage. In other words, if the reverse voltage is too high, the diode breaks reversely to create a path to safeguard the circuit. In case the rectification of high voltage is broken, the high voltage fuse burns out.

3 Symptoms of a Bad Microwave Diode

The following table shows the summary of the symptoms of a bad microwave diode as well as what you can do to fix the problem:  

1.Microwave buzzing and hummingInspect the diode, test it for electrical continuity, and replace it if it fails the continuity test.
2.Microwave not heatingStart by inspecting the capacitor and magnetron because they may also be responsible for making the microwave fail to heat.
3.Microwave is sparkingLocate the diode, inspect it, and test it for continuity. Replace it if there’s no continuity.

There aren’t too many symptoms of a bad microwave diode. The most common ones include sparks & burning smells, the microwave not heating, and the microwave making humming & buzzing.

1. Microwave Starts to Have Heating Failures

Apart from a failed main control board, a faulty fuse cavity, a blown line or thermal fuse, and a faulty door switch, the high-voltage diode could also be the possible reason why the Whirlpool, Kenmore, GE, or KitchenAid microwave is not heating.

Your microwave failing to heat is a perfect sign of a faulty diode, which means you should get a new one for replacement.

2. The Microwave Starts to Pop Sparks

Sparks in your Kenmore, LG, Samsung, or Whirlpool microwave could be a sign that the high-voltage diode is defective.

Also, a burning smell from your microwave can indicate that the diode is bad. A burned-out diode can break into two, wear out, or short.

Immediately locate the diode in the cabinet next to the magnetron and replace it.

3. Microwave Starts to Make Noise

Your microwave could be buzzing and humming because the high-voltage diode is defective.

Apart from the diode, other components that can make your microwave make noise are the plate & drive motor, cooling fan, and magnetron.

Keep in mind that you can’t repair a bad diode. You can only replace it with a new one.

Also Read: Samsung Microwave Touchpad Not Working

How to Test a Microwave Diodes

symptoms of a bad microwave diode

Safety Warning

While repairing a microwave, the chances of falling into electrocution by the high-voltage capacitor even after unplugging the power cord from the socket are very high.

So you need to be very careful when doing the diode test.

To begin with, the high-voltage diode is located close to the high-voltage capacitor. In fact, one of its ends is attached to the high-voltage capacitor. (

And as you know, a microwave capacitor carries high power voltages, which can be quite lethal. It is therefore important to start by discharging the capacitor before getting to the high-voltage diode.

Although the capacitor can store charge for a long time, touching both its negative and positive terminals with a metal screwdriver blade will drain all the charge in seconds.

Testing the Microwave Diode

Before you even attempt to replace the diode on your GE, Whirlpool, or KitchenAid microwave, do a functionality test to confirm your suspicion.

You can visibly confirm the diode is burned-out when you see physical damages.

In case there are physical damages, use a multimeter to test if the diode still has a continuous electrical path.

To test the diode for continuity:

Touch the positive and negative terminals of the high-voltage diode with the multimeter probes.

If the diode test negative for continuity on both of its sides, the diode has failed and will need a new one for replacement.

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How to Replace a Defective Diode on a Microwave

How you get to the high-voltage diode generally depends on the microwave brand and its models too.

To get to the diode on some microwaves:

  • Open the microwave door and unthread the screws holding the vent.
  • Remove the screws holding the control panel in place and detach the panel by lifting it.

There might be an access panel behind the microwave that when removed will give your access to high-voltage to replace it.

Other brands will require you to get rid of the microwave’s cover to get to the high-voltage diode.

With stand-alone microwave brands, things are as straightforward as removing the screws holding the access panel on either side, top, or behind the microwave.

Those mounted to a wall under the kitchen cabinet will need to be first removed from the kitchen cabinet to make the panel easy to access.

Here are simple typical steps to walk you through the process of replacing your microwave’s defective diode:

  • Cut off the microwave’s power supply and unplug its power cord.
  • Open the microwave door, remove the glass tray, and glass tray support.
  • With a friend’s help, remove the screws holding the microwave to the kitchen bracket and wall-mounting bracket.
  • Carefully tilt the microwave, pull the power cord through the cabinet hole, and place it on a sturdy surface with its front facing up (let it lay on its rear panel). 
  • With a screwdriver, remove the screws holding the bottom panel.
  • Disconnect any wire that connects to the bottom panel and set the panel aside.
  • Position the microwave upwards, open its door, remove the screw that holds the venting, and fully take out the venting.
  • Depending on your microwave, remove the screws securing the top, rear, or top cover to the frame.
  • Remove the damper or blower cover if necessary and slide the cover to get the diode and capacitor.
  • Having discharged the high-voltage capacitor detach the diode from the high-voltage capacitor and remove the screws holding the faulty high-voltage diode to the microwave frame.
  • Now, install the new diode by connecting the appropriate end to the high-voltage capacitor and securing the other end of the high-voltage diode, which is the grounding end to the microwave frame.
  • Reassemble the microwave by reconnecting the wires, blower cover, and all the other panels.
  • With some help lift the microwave, reposition it on the mounting bracket, and mount screws to hold the microwave to the kitchen cabinet.
  • Open the microwave door and replace the turntable and its support.

With the diode replacement complete, plug the power cord back into power and start using the microwave.

Also Read: Whirlpool Microwave Fan Won’t Turn On

How Much Does it Cost to Replace a Diode in a Microwave?

Microwave diodes can wear out over time and when that happens, you will see sparks, notice a burning smell, and hear loud hums.

And given that you can’t repair a faulty high-voltage diode, the only option is to replace it with a new one.

Talking of the spare part itself, you will spend anywhere from $5 to $25 for a new diode.

Professionals on the other hand will want you to pay them $50 minimum and $100 maximum to service the same component.

If you do the math, you will need to have $55 to $125 to have the microwave diode replaced.

Fortunately, if you are cautious enough, you can use the steps shared in this guide to replace the diode yourself, which is a great way to save up to $100 in service fees.

Frequently Asked Questions

1. How Do You Know if a Microwave Diode is Bad?

It’s easy to know if Whirlpool, KitchenAid, or GE microwave diode has a problem.

If you see sparks in your microwave, a burning smell, or food failing to heat without forgetting buzzes and hums, it could be a sign that your microwave is having a problem with the component.

2. Which Diode is Used in a Microwave?

Although diodes made of Gallium Arsenide (GaAs) are said to be the best choice for microwaves, most microwaves come with a diode made of silicone.

3. What Happens if Diode Fails in Microwave?

Two things may happen to any microwave if the diode fails:

Your microwave will start making noise, which at some point becomes irritating.

Also, the microwave may fail to heat anything that you put in the heating chamber because the magnetron is not getting any power from the diode. 

4. What Causes a Microwave Diode to Fail?

A microwave diode can stop working if the high-voltage capacitor fails and that is because the diode depends on the capacitor for power.

This explains why you will see one of the diode’s terminals attached to the high-voltage capacitor.

The other reason why the high-voltage diode fails is that a fuse is blown. When a fuse blows, a circuit is broken, and the high-voltage diode fails.

Final Thoughts

A microwave can run without a high-voltage diode, but any food or drink you put into the microwave will come out cold.

In other words, a microwave without a diode won’t heat food because the magnetron is not getting the power it needs to convert to heat energy.

Remember, the work of the high-voltage diode is to transform alternating current (AC) to direct current (DC), which is the only form of energy the magnetron can transform to heat.

So you should replace the diode if the current one isn’t working.

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