Microwave making noise: Common causes & fixes

There’s a strange symphony playing in your kitchen, but it’s not coming from any traditional sources. Instead, it’s your microwave, humming, buzzing, and rattling like there’s a mischievous creature trapped inside. These unexpected kitchen concerts can range from mildly amusing to downright alarming, especially when it’s supposed to be quietly reheating your leftovers, not sounding like a scene from a sci-fi movie.

Don’t worry—your noisy microwave isn’t auditioning for a spot in an orchestra of haunted appliances.

With some detective work and a few handy tips, you’ll be able to quiet down your a microwave that’s making noises and restore the peaceful sound of cooking food.

If you need replacement parts for your microwave, you can enter your model number at AppliancePartsPros.com to find them.

Disclaimer: The troubleshooting information provided in this article is based on general service manuals and may not apply to your specific appliance model. While we strive to offer helpful advice for DIY appliance repairs, variations in models and configurations can lead to differences in troubleshooting steps, error codes and part replacements. For the most accurate guidance, we strongly recommend consulting the technical sheet for your specific appliance model.

Safety tips

Working on a microwave oven requires caution since it contains high-voltage components. Make sure to take these precautions:

• Always power off and unplug your microwave or switch off the circuit breaker before attempting any maintenance or replacement work. This keeps you safe by preventing any risk of electric shock.
• Always discharge the capacitor before working on the microwave.
• If the microwave has recently been used, give it plenty of time to cool down before working on it.
• Take your time and don’t rush while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access microwave parts.
• Keep your workspace free of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with wet hands. Make sure the work area is completely dry.
• Check the user manual to see if there are specific installation or safety instructions related to your microwave or replacement part.
• Be gentle when handling or removing parts. Excessive force might damage the microwave or cause personal injury.
• Wear insulated work gloves to protect your hands from sharp metal parts and debris.
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.
• Consider wearing safety glasses and/or a dust mask when working with chemicals, dust or a large amount of debris to prevent irritation or injury.

Read More: How to use a multimeter

How to safely discharge the capacitor

IMPORTANT: Carefully follow the correct handling and discharge procedures since exposure to the voltage levels inside a microwave can potentially cause severe injury or death. Prioritize safety at all times and follow the instructions and recommendations provided by the manufacturer. If you do not feel comfortable discharging a capacitor, do not attempt to do it yourself.

1. Unplug the microwave from the power source.
2. Grab a screwdriver with good insulation on the handle to protect against electric shock.
3. Gently touch the insulated screwdriver blade to one terminal of the capacitor.
4. Slowly and gently slide the screwdriver forward until it reaches the other terminal of the capacitor. Hold it there for a few seconds. This discharge process often results in a loud and startling ‘POP’ sound.
5. Repeat the process to create a short circuit between each capacitor terminal and the chassis (bare metal mounting plate surface). If the capacitor has three terminals, use the same method.

Common causes of microwave noises

Clogged air vents

If the microwave vents are clogged up with dust or other debris, clean them off with a cloth or soft brush. In some cases, this may be all you need to do to get that normal humming sound back.

Faulty magnetron

The magnetron takes high voltage electricity from the transformer and converts it into powerful microwave frequencies that cook the food that’s placed in the cavity.

A well-functioning magnetron will emit a low-intensity hum during cooking. But if the magnetron is defective or reaching the end of its lifespan, you may hear these types of disruptive noises emitting from it:

• High-pitched whining or whistling sounds
• Buzzing noise
• Humming noise

To evaluate a suspect magnetron, you can test its resistance with a multimeter:

1. Unplug the microwave and discharge the capacitor.
2. Remove the outer panel to access the magnetron.
3. Set your multimeter to test resistance in Ohms (the symbol looks like an upside-down horseshoe).
4. Touch the meter probes to the magnetron’s contacts.
5. Check the reading on the multimeter display.
6. Check the magnetron antenna for signs of damage.

A magnetron should show a very low Ohm reading, usually less than 1 Ohm of resistance. Higher resistance or no resistance means you have a defective magnetron that needs to be replaced.

Read More: How to clean a microwave grease filter

Diode failure

The diode is another important component required for directing the flow of high-voltage electricity from the transformer to the magnetron.

Like the magnetron, the diode operates under high voltages. If it becomes defective, it can also be a source of unusual humming or buzzing noise coming from the microwave.

The diode acts like a one-way valve, only allowing electricity to flow in a single direction to the magnetron. If the diode is faulty, it can result in reverse electrical flows or voltage drops that prevent the magnetron from receiving consistent power.

To test a microwave diode:

1. Unplug the microwave and discharge the capacitor.
2. Remove the diode from the circuit.
3. Use a multimeter and 9V battery as a power source.
4. Check diode voltage in both directions. You can do this by placing one diode terminal onto one of the battery posts. Then test from the other terminal end to the open battery post. Reverse the diode terminals you used and test for voltage again. There should be 9V shown on only one terminal when testing from the diode terminal to the open battery post.

A properly working diode will show voltage in only one electrical direction. If the diode shows voltage in both directions, it’s defective and needs to be replaced.

Read More: How to change a microwave light bulb

Turntable motor problems

The motor that rotates the glass turntable is another prime suspect behind unusual humming, buzzing, or knocking noises coming from your microwave.

The turntable motor is responsible for spinning the tray at a consistent pace so food cooks evenly. If the motor bearings are worn out or its windings are damaged, you may hear abnormal noises as the turntable struggles to rotate.

Be cautious when working near the magnetron, diode, and transformer if you’re exposing the turntable motor. Avoid direct contact with any high-voltage components.

To troubleshoot the turntable motor:

1. Remove the bottom panel.
2. Set the multimeter to VAC.
3. With a moist cloth in the microwave, start a cycle.
4. Test the motor for 120 Volts AC. Once you identify the presence of voltage, turn the microwave off.

If you get a reading of 120 Volts AC and the turntable doesn’t rotate and the coupling isn’t damaged, the turntable motor needs to be replaced.

Watch: How to replace a microwave turntable motor

Cooling/exhaust fan issues

Microwave ovens require internal air circulation and ventilation to prevent overheating. A defective cooling fan or a faulty exhaust fan motor can cause buzzing, rattling, or grinding noises while the microwave is running.

How to troubleshoot:

1. Make sure all vents are clear of obstructions.
2. Find the exhaust fan motor and other cooling fan motors.
3. Remove each fan and try spinning the blades with your fingers. If the blades don’t spin freely or if they scrape loudly, the fan needs to be replaced.

Control board or other component malfunctions

It’s less common for loud or unusual microwave sounds to come from the control board or other components like sensors, switches and controls, but it can happen.

How to troubleshoot:

• Test the buttons following your model’s testing procedure.
• Make sure the door sensors and switches are correctly triggered.
• Inspect the control board for damage.
• Swap out the suspected faulty control board with a known working control board to see how your microwave works.

Read More: How to replace a microwave turntable coupler

More information

Thank you for reading! We hope this guide helped you repair your microwave and get it running quietly again.

If you have any other appliance repair needs or projects, don’t hesitate to explore our thousands of free videos and troubleshooting guides available. If you need replacement parts or some extra help, grab your model number and head over to AppliancePartsPros.com, where you can chat with a pro, order parts, read our DIY blog, and more. We can also help you troubleshoot common microwave problems here.

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