Microwave Buzzes Then Stops Working: How to Fix It

A buzzing sound emanating from your microwave can be a sign of various issues, and it often coincides with a microwave that doesn’t work properly. If you’ve recently noticed a loud buzzing noise and reduced functionality, this article will outline the most likely causes.

Not only will we help you identify the source of the problem, but we’ll also explain what steps you can take to fix the issue. Keep reading to learn why your microwave buzzes and then stops working.

WARNING: Repairing microwaves is dangerous, as the high-voltage capacitor can hold a lethal charge even when the microwave is unplugged. To ensure safety, it’s recommended to discharge the capacitor before starting any repairs. Safely discharge the capacitor by wearing rubber gloves and using an insulated screwdriver to carefully bridge the capacitor terminals.

Why Your Microwave is Buzzing and Not Working Properly

If your microwave makes a loud buzzing or humming noise and isn’t working properly, check these three key areas for potential issues:

Failing Magnetron

The magnetron generates the electromagnetic waves that cook your food. However, when this key component is on its way out, it can emit a louder-than-usual buzzing sound and fail to heat your food.

Your microwave may continue to run with a faulty magnetron, producing a continuous loud buzz, or it may buzz briefly when you attempt to use it and then stop working.

Unfortunately, a faulty magnetron cannot be repaired and must be replaced, and this component isn’t cheap. Follow these steps to replace a failing magnetron:

1. Unplug the microwave.
2. Remove the outer casing of the microwave. You will need to remove the screws securing it.
3. Safely discharge the high-voltage capacitor.
4. Locate the magnetron. It looks like a metal box.
5. Disconnect the wires connected to the magnetron and remove the screws securing it to the frame. Carefully lift it out of the microwave.
6. If you are unsure if the magnetron is faulty, you can test it with a multimeter for continuity.
7. If faulty, purchase a new magnetron and install it in the same position as the old one. Be sure to secure it with all the screws and connect the wires correctly.

Defective High-Voltage Diode

The high-voltage diode converts AC power to DC power, which is required to generate the high voltage needed to operate the magnetron. However, if the diode blows, the result can be a buzzing sound and a microwave that doesn’t heat.

A faulty diode is not repairable and requires replacement. Follow these steps to do so:

1. Unplug the microwave.
2. Remove the outer casing of your microwave.
3. Safely discharge the capacitor.
4. Find the high-voltage diode, typically connected to both the capacitor and the magnetron.
5. Disconnect the high-voltage diode from its terminals and remove it.
6. With a multimeter set to diode test mode, place the black probe on the diode’s cathode and the red probe on the anode; the reading should be between 0.3V and 0.7V. Next, reverse the probes (red on the cathode, black on the anode); the reading should be OL.
7. If the reading deviates from this, it’s faulty and needs replacing.
8. Purchase a new diode and place it in the same position as the old one, ensuring it connects to the right terminals.

Faulty Cooling Fan

The cooling fan keeps internal components like the transformer and magnetron cool. If the fan is damaged, loose, or obstructed, it may make a buzzing, rattling, or whirring sound.

You can check the cooling fan by following these steps:

1. Unplug the microwave.
2. Remove the microwave’s outer casing.
3. Safely discharge the capacitor.
4. Locate the cooling fan near the magnetron.
5. Inspect the fan for damage, such as cracked or missing blades. Look for obstructions, like caught hair or debris, and check if the fan is loose. Manually spin the fan to see if it scrapes or grinds.
6. If dirty, clear any obstructions.
7. If damaged, remove the cooling fan by unscrewing any mounting screws, disconnecting its wires, and lifting it out. Then, install the new fan in its place.

A Stuck or Faulty Door Interlock Switch

A stuck or faulty door interlock switch can cause a microwave to buzz and not work properly. That’s because the door interlock switches tell the microwave when the door is shut, and do not let it run if it’s not.

As a result, if a door interlock switch is faulty or stuck, the microwave may attempt to run (causing the temporary buzzing sound) but then stop because the faulty interlock switch prevents it.

You may be able to free a stuck interlock switch by tapping near the latch with your hands. However, this tends to be a temporary solution, and you may damage your appliance in the process.

To permanently fix this issue, follow these steps:

1. Unplug the microwave.
2. Remove its outer casing.
3. Discharge the capacitor.
4. Locate the door interlock switches near the door latch mechanism.
5. Inspect the switches for signs of damage and obstructions.
6. Disconnect the wires from an interlock switch and test it with a multimeter. A good switch should show continuity when pressed and none when released.
7. Repeat this test on all the door interlock switches.
8. Replace any faulty switches by unscrewing them from their mount. Install new switches in the same position and reconnect the wires as they were.

Summary

It’s not always simple fixing a microwave that is making a buzzing sound and not working properly. That’s because it often involves replacing internal components such as the magnetron and high-voltage diode. Fixing microwaves is also inherently dangerous, so if you’re not well-versed in appliance repairs, consider hiring a professional to fix it for you safely.