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A stainless microwave hood combination under wood wall cabinets, running with its side-hinged door with a mesh window closed and the microwave cavity lit, a plain glass bowl on the glass turntable behind the mesh, a faint shimmer of vibration suggested only by a spoon resting on the counter below out of focus.

Loud Hum, Buzz or Grinding From a Microwave

A microwave making loud noise may hum deeper and harsher than it used to, buzz only when heating starts, grind under the glass tray, rattle from the fan, or squeal at the start of each cycle, and each sound belongs to a different part.

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Mon–Sat, 8am–8pm

  • 5 checks before you book
  • 5 questions that narrow it
  • 6 causes, cheapest first

Book a visit

Three short steps, about a minute.

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What it
usually means.

A microwave always hums while it heats: the high-voltage transformer vibrates at the frequency of household current, and the cooling fan and turntable motor add their own sounds. What matters is a change. A loud, rough buzz that begins only when heating begins belongs to the high-voltage chain: a magnetron failing, a diode or capacitor breaking down, or a transformer loose in its mounts. A rattle or grind that runs whenever the unit is on belongs to a fan with a bent blade, a cooling fan with dry bearings, or the turntable motor and its roller ring. On a hood combination the vent fan is a source of its own: a damper flapping in the duct, a blade rubbing its housing, loose mounting bolts, or filters sitting loose in their slots. A sharp crackle or snap is not a noise problem at all but arcing, which has its own page. When the sound starts and stops is the most useful thing an owner can notice; the parts behind the loudest buzz sit inside the outer case with the charged capacitor.

A technician in a plain gray work shirt stands at a stainless countertop microwave on a kitchen counter in a US home, reading a digital probe thermometer in a clear glass measuring cup of water he has just taken out of the open microwave, the microwave's glass turntable visible inside. The 6 causes, cheapest first

Answer these first

01

Does the noise start only when heating starts, or whenever the fan, light or turntable runs?
02

Is it a steady deep buzz, a rattle, a grinding, a squeal, or a crackle?
03

On a hood combination, does it come with the vent fan alone while the microwave is off?
04

Does the microwave still heat normally while it makes the noise?
05

Does the sound change or stop when the glass tray and roller ring are taken out?

Check these
before you book.

Microwave making loud noise: 5 checks, and none of them costs anything.

01

If the noise is a crackle or snap with flashes inside, stop the cycle; that is sparking, not a sound to diagnose.

02

Stop using it if a loud buzz comes with weak heating or a burning smell.

03

With the unit off, lift out the tray and the roller ring, clean them and the floor under them, and set them back.

Also worth checking

  • On a hood combination, run the vent fan alone with the microwave off, and make sure the grease filters are clipped in.
  • Tell us when the sound starts and stops, and send the model number from the label inside the door frame; a short video of the sound helps.

How soon does it need a visit?

A new, loud buzz during heating, especially with weaker heating, is a reason to stop using it and book a visit. Please do not run it empty to listen: with no load inside, the energy goes back into the part that is already failing.

The causes,
cheapest first.

6 things loud hum, buzz or grinding from a microwave turns out to be, from the ordinary hum of the transformer to magnetron failing.

The cost guide
  1. 01 no repair

    The ordinary hum of the transformer

    A steady, even hum during heating is how every microwave sounds. It becomes a question only when it grows louder, rougher or uneven.

    No repair: check it yourself
  2. 02 low

    Roller ring or turntable motor grinding

    A dry, dirty ring or a worn motor grinds under the tray. Cleaning the ring and the cavity floor often quiets it; a motor that still grinds is replaced.

    Fixed by microwave turntable and motor repair
  3. 03 low to moderate

    Vent fan blade, damper or loose filter

    On a hood combination, a filter not clipped in, a damper flap in the duct, or a blade rubbing its housing rattles with the fan and not with heating.

    Fixed by microwave vent fan and filter repair On a microwave hood combination
  4. 04 low to moderate

    Cooling fan bearings running dry

    The small fan that cools the magnetron squeals or grinds as its bearings dry. Left alone, it slows and the unit begins to shut off from heat.

    Fixed by microwave vent fan and filter repair
  5. 05 moderate

    High-voltage diode or capacitor breaking down

    A diode or capacitor on its way out makes the transformer labor, and the hum turns to a heavy buzz, sometimes followed by a breaker trip.

    Fixed by microwave high-voltage diode and capacitor repair See microwave trips the breaker or blows a fuse
  6. 06 moderate to highest

    Magnetron failing

    A loud buzz or growl during heating, with food heating slower or not at all, is the classic sound of a magnetron near its end.

    Fixed by microwave magnetron repair

The makes
it happens on.

18 makes on this site; loud hum, buzz or grinding from a microwave can show up on any of them. Each mark opens that make's own page.

All 18 brands

Loud Hum, Buzz or Grinding From a Microwave,
where we come out.

9 metros, each with its own page.

All service areas

Tampa BayFL · 31 areas

OrlandoFL · 30 areas

Miami / South FloridaFL · 47 areas

New York MetroNY · 75 areas

HoustonTX · 36 areas

ChicagoIL · 50 areas

Los AngelesCA · 95 areas

San DiegoCA · 31 areas

San Francisco Bay AreaCA · 74 areas

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For the heart of your home.

Questions about
loud hum, buzz or grinding from a microwave.

How loud should a microwave hum?
Loud enough to hear in a quiet kitchen, steady and even. A change is the useful sign: louder, harsher or rougher than it was means something has shifted.
Why does my microwave buzz but not heat?
The high-voltage chain is working hard and producing nothing, and a failed diode, capacitor or magnetron is typical. Stop using it until it has been checked.
The fan above my cooking surface rattles. Is that the microwave?
It is the microwave's own vent fan or its damper. Clipped-in filters and tight mounting cure many rattles; a blade that rubs or a motor that whines needs a visit.
Is grinding from the tray harmful?
Not dangerous, but it wears the coupler and the motor. Clean the roller ring and the floor under it first, and book a visit if the grinding stays.

Back to your everyday

Still seeing loud hum, buzz or grinding from a microwave?

Book with what you checked above — 5 answers save the technician the first part of the visit.

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