Microwave makes a loud humming or buzzing noise

Symptoms

• Loud buzzing or humming during operation
• Noise may be louder than what you remember from before
• May be constant or intermittent during a cycle
• Food may or may not still be heating

Likely causes

• CommonAging high-voltage transformer or magnetronThese components can develop a louder hum as they age, even before fully failing.
• PossibleWorn turntable motor bearingA failing small motor can create a buzzing sound distinct from the main hum.
• PossibleLoose internal panel or part vibratingA loose screw or panel can rattle and sound like a buzz.
• PossibleCooling fan issueA fan with debris or a failing motor can create noise separate from the heating hum.

What to do

1. Note whether the noise happens throughout the whole cycle or only at certain points, like right at start-up.
2. Check if food is still heating normally despite the noise, which helps distinguish a cosmetic annoyance from a failing magnetron.
3. Look at the exterior vents for obstructions that might be making the cooling fan work harder and louder.
4. Gently check (with the unit unplugged) that the outer case doesn't have any obviously loose panels you can safely tighten.
5. If the noise is new, getting louder, or paired with reduced heating, treat it as a sign of a component wearing out.
6. For noise from the high-voltage section, don't attempt to open the case; have a technician assess it.

Tools and parts

• Screwdriver

When to call a pro

If the noise is new or getting worse, especially alongside weaker heating, have a technician inspect the magnetron, transformer, and turntable motor.

Safety