Microwave is very noisy during operation (loud humming, rattling, or buzzing).

Safety first: Unplug the microwave before any inspection. Do not touch high-voltage components.

• Isolate noise source: Run the microwave with a cup of water and listen carefully to determine if the noise is from the top, side, or bottom.
• Check external items: Ensure the microwave is level and not touching adjacent cabinets or objects that could vibrate.
• Turntable test: Run the unit briefly with the glass tray removed (if allowed by the manual) to see if the noise changes. If it does, inspect the tray, roller ring, and coupler.
• Internal components (advanced): If the noise is from the rear or top, the cooling fan or magnetron may be failing. Accessing these parts requires removing the cabinet and should be done by a technician.
• Next step: Persistent loud buzzing or rattling often indicates a failing magnetron or fan motor; schedule professional service.