If you are facing that your microwave is not working for some reason, suppose your microwave is not getting hot, this will simply mean that the Capacitor is bad. But to be sure you have to begin with, unhook the lines that link to the microwave and remove the entire Capacitor gently. 

Set the continuity test on the multimeter. Because the Capacitor is made up of two independent metal plates inside, it is negative if it shorts. And if the metal plates meet, the Capacitor ceases to operate as a capacitor and instead functions as a massive wire, which is a bad thing that simply signals that the Capacitor is defective.

I will give 7 symptoms of a bad microwave oven in this article and more.

7 Symptoms Of A Bad Microwave Capacitor

symptoms of a bad microwave capacitor

By now, you already know what a capacitor is, but for some reason, if you find your microwave is not working properly, then these might be the symptoms of a bad capacitor:

  1. Sound- Your appliance will make a lot of buzzing noise while operating, which it normally does not make. 
  2. Stop working- You might find that your microwave stops working suddenly and doesn’t start operating any time soon. 
  3. Circuit failure- Circuit breakers fail due to short circuits, spikes, power surges, circuit overloads, and conduit systems with grounded wires. So if you see that your high voltage circuit has failed, it might be because of your bad microwave capacitor.
  4. Heating- One more thing might happen because of a bad capacitor: your microwave won’t heat any of your foods. That means if you put food in your oven despite working, your food won’t get hot. 
  5. Blow a fuse- Any unanticipated electric event that results in a power outage can be caused by a bad capacitor. So, if you happen to have seen that the main fuse of your microwave has blown up, it is because of a bad capacitor.
  6. Not starting- Because of a bad capacitor, your microwave might not start or work at all. So, don’t panic if your microwave does not start. 
  7. Overheating- Suppose the outer layer of your microwave is way too hot that you can’t even touch it. So, you might be wondering what went wrong. A bad capacitor is an answer to your given question. 

What Is A Microwave Capacitor?

Before going further, you must first know what a microwave capacitor is. Therefore, let me give you the answer. 

Microwave capacitors are used in simple and complicated filter architectures as tuning elements or components. A large tolerance is generally required when a low capacitance value is used as a tuning element. When used as a DC block or bypass, the only thing that matters is that your RF signal encounters a low impedance.

What is the Function of a Microwave Capacitor?

As 120 volts is insufficient to operate a magnetron, a microwave oven’s high voltage capacitor, in combination with its diode, significantly increases the voltage or charge that reaches the magnetron from a residential wall socket. As a result, it is an essential element of the appliance’s basic functionality.

A diode is a relatively easy component to replace. Other DIY projects, such as changing out charcoal filters, are even easier. On the other hand, the high voltage capacitor in a microwave is dangerous to change yourself. On the other hand, testing its functionality will help you decide whether to fix it yourselves, hire a professional, or replace the complete microwave.

How To Check A High Voltage Capacitor In A Microwave?

When it comes to analyzing your microwave’s Capacitor, a few methods are often less trustworthy or harder to read, so the best two approaches are simple visual examination and the use of a multimeter. An ohmmeter can be used occasionally, although a digital multimeter is preferable.

Advice from an expert

Though capacitor discharging pens are available, you don’t need one to perform a discharge.

Unplug the microwave oven and thoroughly discharge the Capacitor before troubleshooting, repairs, or replacements to avoid a harmful electrical shock from contacting metal components. Also, be sure that there is no liquid in your workspace.

How To Fix A Microwave Capacitor?

Since the high-voltage Capacitor is close to the magnetron, you’ll need to disconnect the microwave and eliminate the housing to get to it.

You’ll need a particular VOM meter with capacitance testing capabilities. However, any accumulated electrical charge needs to be released first before testing. Injury may ensue if you do not do so.

Touch each tip to the Capacitor’s terminals with insulated pliers. When releasing the accumulated electrical charge, be very cautious not to unintentionally touch any metal plier component.

If the Capacitor in your microwave fails, you’ll need to replace it because you won’t be able to repair it. 

Watch this video about “Faulty Microwave Capacitor Diagnosis and Replacement” from “Tanner Tech

What is the Visual Method for Testing a Microwave Capacitor?

For access and discharge of the Capacitor, you’ll need a head screwdriver with rubbery handles and gloves.

Check the Capacitor’s connection points, casing, and terminals for any visible evidence of damage, such as electrical burns, after you’ve accessed and discharged it.

You’ll have to change your Capacitor if you see any obvious damage.

How To Test A Multimeter Method Of A Microwave Capacitor?

A head screwdriver with a rubber sole grip, a multimeter (ideally digital), and rubber work gloves are all required tools.

If there isn’t any noticeable damage to your Capacitor, the next step is to test it using a multimeter. Make that the equipment is disconnected and that a capacitor discharge has been done. Steps to follow are given below:

  1. Set the multimeter to the Ohmic setting and the resistance to at least 1000 Ohm (1k).
  2. Link the multimeter’s probes to the capacitor end-stage in the following order: Negative to Negative and Positive to Positive.
  3. Please note the values displayed by the multimeter.
  4. After that, the multimeter will default to Open Line (OL) or infinity.
  5. Step 2 is repeated, and the results are recorded.
  6. Your Capacitor is in good functioning order if you get measurements every time and then the OL or infinite reading right away.
  7. If the readings do not change or display 0, your Capacitor is dead and has to be replaced.

How Much Time Does It Take To Discharge A Microwave Capacitor?

If the inner resistance is ten megohms and the Capacitor is little more than one microfarad, the time to charge to a stable voltage will still be on the order of several tens of seconds. If you let your microwave sit overnight, the cap ought to be dead.

What Happens If You Don’t Discharge The Microwave Capacitor?

Discharging the Capacitor in your microwave is critical for avoiding damage to your microwave, your appliances, and yourself. Even when your microwave is disconnected, a capacitor retains significant amounts of electricity and must be discharged before any repairs can occur.

If A Microwave Capacitor Fails, What Happens?

A faulty high voltage capacitor could possibly be to blame for the oven’s inability to heat up. Any issue with the HV capacitor will impact the entire high voltage circuit’s operation.

What Is A Single-Layer Capacitor?

For the best frequency response, single-layer caps are the way to go. When created monolithically, thin-film capacitors, also known as thin-film capacitors, can be employed in microwave circuits far beyond W-band (110 GHz). TFCs are utilized as bypass, DC blocking, and RF adjusting elements in MMICs and RFICs.

It all boils down to how successfully you can regulate the dielectric thickness in a good process, delivering +/-10 percent precision. Silica nitride and silicon are the most common dielectrics. The top limit for capacitors on MMICs is on the order of 20 pF.

Metalizing a substrate, covering it with a thin dielectric, and then applying a top metal to form a sandwich is how TFC is made. MIM (metal-insulator-metal) caps are another name for them.

What Is A Metal Oxide Semiconductor Capacitor?

The silicon revolution resulted in the development of these capacitors. Growing silicon oxide isolates silicon circuits. You can make a capacitor by putting a layer of metal on top (usually always aluminum in a silicon process). This Capacitor gives outstanding microwave responsiveness for values up to hundreds of pF.

MOS caps differ from MIM caps because the “base metal” is a semiconductor (silicon) that offers electrical contact through the backside. A MOS cap’s backside might be plated with aluminum or left unplated. MNS is another version on this topic (metal nitride silicon).

What Is An Electrolytic Capacitor?

Electrolytic capacitors have the maximum density with capacitance levels in the tens of microfarads. Tantalum is frequently used. Although these are not microwave-quality, they are commonly utilized as power supply filtering for microwave circuits.

To stay stable, linear regulators require at least two electrolytic caps, one on the input and one on the output. Electrolytics are set in banks in pulsed applications to offer charge storage and manage voltage droop. Because electrolytic caps are polarized, you must be careful while connecting DC voltages across them. They could set off the smoke detector if you bias them backward!

What Happens If You Don’t Use A Microwave Capacitor?

The glass turntable (which also serves as a sacrificial load) gets heated initially. This prevents damage if the time is less than 5 to 10 minutes. After that, things become a little more exciting, with the turntable glass melting, the mushroom-shaped drive arcing out, and the crystal plate and magnetron being damaged.

Even though the magnetron and inside vent have thermal cutouts, they sometimes don’t cut power in time. Also, any dirt or grease inside the cabinet will be mistaken for food, causing a fire.

In A Microwave, What Kind Of Capacitor Is Used?

Surface-mount multilayer ceramic capacitors are utilized in microwave printed wiring boards and DC filtering in hybrid integrated circuits. High capacitance in a small volume is possible because of multilayer technology. Multilayer capacitors in sizes 0402, 0603, and 0805 are commonly used in microwave applications.

What Is The Voltage Rating Of A Microwave Capacitor?

A microwave’s high voltage capacitor is measured in microfarads, and that’s one or less and can handle up to 2100 volts. On the side of the Capacitor, you’ll find that reading on a tag.

Is It Possible To Replace A Microwave Capacitor With One With A Higher Uf?

It can be higher, but it must never be lower, or you will have to replace it shortly. Then there’s the uF rating: The Capacitor in a microwave, unlike a traditional power supply filter capacitor, is in a voltage doubler and is effectively in series with the load (magnetron).


Symptoms of a Bad microwave capacitor have been thoroughly answered, along with a few other key details. Hopefully, this article of mine has responded to most of your questions. 

So now that you know everything about microwave capacitors, I believe it will be much easier for you to identify if your Capacitor has gone bad or not. As a person who uses a microwave in your day-to-day life, it is obvious that you will have queries about it. So, I am glad that it was helpful for you to learn new things about microwave capacitors.

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