LG Microwave Unusual Noise? Causes & Fix

Most Likely Cause#

An unusual noise from an LG microwave matters less for what it is than for how urgent it is. Some sounds — a popping or crackling arc, a sharp electrical snap — mean stop and unplug immediately, because they signal arcing inside the cavity or a high-voltage component breaking down. Others — a faint hum, an occasional click — are normal and need nothing. The trick is placing your noise on that urgency scale first, then chasing the part. The most common genuinely-abnormal sound is a rising screech or squeal, which usually traces to the magnetron or a drying-out fan bearing.

So before you troubleshoot, triage. If the noise comes with sparks, smoke, or a burning smell, this is a stop-now situation. If it is merely new or louder but the microwave heats and behaves otherwise, you can investigate at your own pace.

Safety first: if you hear popping, crackling, or arcing and see sparks or smell burning, stop the microwave and unplug it now. Do not run it again until the cause is found. The high-voltage capacitor inside can hold a dangerous charge even when unplugged, so never open the cabinet yourself.

Rank the Noise by Urgency#

• Stop immediately: popping, crackling, or arcing sounds, especially with visible sparks or a burning smell. These point at arcing in the cavity — a damaged waveguide cover, metal in the oven, or food splatter — or a high-voltage failure.
• Investigate soon: a rising screech, squeal, or loud drone that grows over weeks, often alongside weaker heating. This points at the magnetron or its cooling fan.
• Monitor: a faint hum at idle or a click as power levels change. These are usually normal operation.

What Usually Causes It#

The table pairs each abnormal sound with its likely source.

Arcing Sounds#

Popping and crackling are the sounds to respect. Inside the cavity, they usually mean the waveguide cover has burned or a stray piece of metal or dried food is sparking. With the microwave unplugged, inspect the small waveguide cover on the cavity wall for scorching and clean the interior; a charred cover must be replaced before running the unit again. If arcing continues after cleaning and cover replacement, the fault is deeper in the high-voltage section and needs a technician.

Screech, Squeal, and Drone#

A noise that climbs in pitch or volume over time, especially when your food is also heating more slowly, points at the magnetron aging out or, on inverter models, the high-voltage side straining. On over-the-range units, a whine that appears when you run the exhaust fan is instead a fan-motor bearing drying out. Isolating the fan by running it alone tells the two apart quickly.

Quick Diagnostic Sequence#

1. Triage: any arcing, sparks, or burning smell means unplug now and stop.
2. With the unit unplugged, inspect and clean the cavity and the waveguide cover.
3. Run the exhaust fan alone to isolate a fan-bearing whine.
4. Note whether a screech or drone tracks with weaker heating.
5. If arcing or a heating-side noise persists, plan a high-voltage inspection.

Repair or Replace#

Cleaning the cavity and replacing a burned waveguide cover are inexpensive fixes. An exhaust fan motor is a moderate part. A failing magnetron or a high-voltage fault is the costly repair, and because it lives on the lethal side of the microwave, an older over-the-range unit with those symptoms is often better replaced than repaired. Whenever the noise is arcing or clearly on the cooking side, do not open the cabinet — book an inspection instead.

FAQ#

Below are the questions we hear most about an unusual noise from an LG microwave.