What you are looking at
A microwave makes a fan noise, a turntable noise and, on many models, a distinct hum from the high-voltage side — so a new noise is best identified by when it happens rather than by how it sounds. On a Criterion debris or a worn roller ring under the plate comes first, because a value-tier build puts the cheap wearing parts — filters, hoses, seals, screens — in the path of everything the machine does, so they are where the fault usually is. Turntable, fan grille and loading checks are owner work; anything that buzzes, arcs or grinds inside the cabinet is not.
What you observe
- A loud buzz that coincides with cooking — The high-voltage side, and a reason to stop rather than to investigate.
- A rattle that stops when you press the cabinet — Panels or a loose grille.
- Crackling or popping with visible flashes inside — Arcing — stop the oven immediately.
- NEAR MISS — Popping from the food itself — Steam escaping from food, not a fault.
Why it happens, in order
- Debris or a worn roller ring under the plate — Most likely here: a value-tier build puts the cheap wearing parts — filters, hoses, seals, screens — in the path of everything the machine does, so they are where the fault usually is. Crumbs and dried spills under the turntable make the plate grind, and the roller ring itself wears and starts to drag.
- A vent grille or panel resonating — Second on the list: Cabinet panels and vent grilles buzz when the fan or the transformer excites them, which sounds far worse than it is.
- Arcing from a soiled waveguide cover or metal in the cavity — Third on the list: Arcing crackles and flashes; it is caused by food residue on the waveguide cover, damaged cavity paint or metal in the oven. It sits here rather than higher because the door hardware is light, so it goes out of adjustment before anything electrical does.
- A cooling fan with a worn bearing or an obstruction — Fourth on the list, and the least likely: The fan runs whenever the oven does; a bearing on its way out gives a rising whine that is present from the moment it starts. The drivetrain is simple, which makes it durable — it is a real cause but rarely the first one.
Check in this order, and why
- Lift the plate out and turn the roller ring by hand — Grit under the ring or a wheel that will not turn freely explains the noise immediately. Start here: on this platform it is both the most likely finding and the quickest to confirm.
- Press gently on the cabinet and the grilles while it runs — A noise that changes under a hand is panel resonance rather than a mechanism.
- Stop the oven and look at the waveguide cover and the cavity walls — A burnt or stained cover, or chipped paint, is the usual cause and the oven should not run until it is addressed.
What to try before calling
- Remove the plate and ring, wash both, and clean the cavity floor — Make sure the plate sits properly on the coupler when it goes back; a misplaced plate grinds and walks.
Tools: clothAbout 15 min
- Check the oven is standing level and clear of anything that can rattle against it — A built-in oven should sit squarely in its housing with its ventilation slots unobstructed.
About 15 min
- Stop here if the next move needs a meter on live terminals — That is where an owner check ends and a service call begins.
Read this before you start
Safety
Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. Nothing here asks you to take the outer cabinet off, and a door interlock is never taped or defeated.
The line between DIY and a callout
Call for anything that arcs, anything that buzzes loudly in time with cooking, and anything that continues once the turntable, plate and grilles have been cleared — and stop using the oven until it has been seen if it arcs.
Nearest pages of this class
How specific this page is
Everything above is generalized across the Criterion microwave range rather than tied to a model. No family- or model-specific page exists beneath it yet; when one is published it will be linked here and it will outrank this page for a named model. Deliberately not here: wiring colours, resistance values, torque figures and part numbers, which differ between families.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
