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Symptoms of a Bad Microwave Capacitor

Since the microwave is now an indispensable kitchen device in many modern homes, nobody likes to have a microwave that doesn’t heat or cook food. This is comparable to having no microwave at all. Therefore, you must know basic skills to troubleshoot any faults as a microwave owner. 

If you notice the microwave producing sparks, the display not functioning, the turntable not turning, not heating food, and so on means that it’s faulty. Therefore, check the capacitor, which is usually the primary cause of most microwave failures.

This article simplifies work by explaining the symptoms of a bad microwave capacitor, how to remove it, and how to resolve it.

Microwave Capacitor

The microwave capacitor is a device that doubles the power to the magnetron cathode (a solid metal rod) from the wall socket. This helps in generating sufficient heat needed for cooking or warming up dishes. 

A microwave capacitor stores a certain amount of charge of up to 3000 volts. This is why you should discharge the capacitor before attempting to fix any faults so you won’t be electrocuted.

Signs of a Bad Microwave Capacitor

A microwave capacitor doesn’t just become bad; various issues make it faulty. Pin-pointing the following problems is vital in evaluating how you will troubleshoot your microwave.

Blown fuse

The microwave’s main fuse protects its components from being blown off due to power fluctuations. Therefore, the microwave won’t work correctly if the power supply is not steady.

A bad capacitor can bring about uncommon fluctuations in power, which can make the main fuse blow up.


The microwave body is usually warm when you operate it, but the oven is defective when it becomes too hot to touch. A faulty microwave capacitor may be the reason why you are experiencing unusual overheating on the exterior body. 

Circuit failures 

Any problem in your microwave coming from the capacitor means only one thing, the whole high-voltage circuit will be affected. That is, the power from the capacitor to the magnetron and the turn table isn’t working as it should. This means you won’t warm or cook food no matter how hard you try restarting the microwave.

Buzzing noise

When heating or cooking food, do you notice an irritating buzzing noise from the microwave? This indicates that the microwave capacitor is already bad or in the process of getting bad.

Fails to heat food

A microwave features a diode that converts the A/C current from the main switch to DC at very high voltages of 5000V. The high voltage through the magnetron provides enough cooking energy in the oven.

If the diode fails, then the microwave won’t heat food. It’s also vital that you never run your microwave empty as this tends to burn the magnetron. 

Stops working

If the microwave is used according to its manual, it’s not supposed to fail. But if the oven stops working suddenly, the capacitor is bad and must be fixed.

Doesn’t start

The capacitor ensures a steady power supply to the other parts of the microwave for efficient functioning. If the microwave doesn’t start, check the capacitor before looking for other problems. 

Cooks and heats food slowly

A faulty capacitor makes the magnetron not receive insufficient power; this reduces the magnetron’s ability to supply the high heat needed for making the food hot. Reduction in heat intensity makes the microwave unable to reheat or cook food. 

How To Test a Microwave Capacitor?

Testing a microwave capacitor involves two issues; checking its physical and voltage conditions. But the capacitor has to be discharged before you examine its visual status.  

Use needle pliers, a screwdriver with rubberized handles, or the capacitor discharger pen to remove the capacitor. However, ensure you have rubberized gloves to protect your hands.

1. Visual testing of a microwave capacitor

After removing the capacitor, check for damage to the chassis or contact points, like electrical burns or rust. If you find any physical damage, you must replace the capacitor, but if there’s none, the capacitor may still be suitable.

2. Voltage testing

Since the physical checkup on a capacitor can’t show if the internal parts are malfunctioning, it’s recommended that you also do a voltage check. This can be done quickly with a digital multimeter or ohmmeter. 

Steps For Testing a Microwave Capacitor Voltage

  1. Put on protective gloves and take the multimeter.
  2. Put the ohmic mode and adjust the resistance to 1000 ohms.
  3. Put the multimeter probes on the capacitor terminals, negative to negative and positive to positive.
  4. Take the voltage readings and note them down.
  5. After that, the multimeter resets to infinity or Open Line (OL).
  6. Repeat the 3rd step to see if the multimeter screen will show the voltage readings again, then take you back to OL
  7. The readings on the multimeter should change, indicate 0 or show an error. If not, then your microwave capacitor is dead.

Can I Repair My Microwave Capacitor?

The capacitor is made in such a way that it adjusts and amplifies the voltage of not only a microwave but also any other electrical appliance. A damaged capacitor, whether from the outside or inside, can’t be repaired. Hence, the only solution to a bad capacitor is to get a new one with the same specs and replace it.

Fixing a Microwave Capacitor 

If you can fix a microwave capacitor, that’s nice and cheaper. But if you can’t, call a technician to do it for you. This is because your safety and that of the appliance are needed.

If you make it a DIY project, discharge the bad capacitor using protective and remove it. Afterward, you can install the new capacitor, which should make your microwave operate normally.

A capacitor is an essential tool in the microwave. A bad capacitor can make your microwave not function as it should. Thus, identifying if the capacitor is the root cause is equally important in preventing extra damage. A faulty capacitor can’t be repaired no matter how small the problem is, and it has to be replaced.