Microwave runs but makes a loud buzzing or humming noise that is much louder than normal during cooking.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety: Unplug the microwave before inspecting any panels. High-voltage components inside are dangerous and should not be handled by untrained users.
User-level checks:
- 1. Compare with load: Test with a full cup of water. If the noise is loudest under load and accompanied by poor heating, the magnetron or HV circuit may be failing.
- 2. Check for loose external panels: Gently press on the sides, top, and door (without blocking vents) while the unit runs. If the noise changes, a loose panel or trim may be vibrating; tighten accessible screws.
Technician-level actions:
- 3. Inspect transformer and magnetron mounts: With the cover removed, ensure the transformer and magnetron are firmly bolted to the chassis.
- 4. Test HV components: Evaluate the magnetron, diode, and capacitor for electrical faults and replace as needed.
If the noise is new, very loud, or accompanied by burning smells or arcing, stop using the microwave and arrange professional service.