The short answer
On a Maytag microwave, a loud buzz with no heating most often comes down to a failed magnetron. Maytag over-the-range units share the Whirlpool interlock stack, so the door switches are the first thing to test on a no-start. The first check below is still an owner check, and the list stops where a meter on live terminals begins.
What you observe
- The turntable turns and the light works, but food stays cold — Everything except the high-voltage side is working.
- It heats weakly and takes far longer than it used to — Partial output, which is a different fault from none at all.
- A loud buzz or hum while it runs — The high-voltage side under strain.
- NEAR MISS — it will not run at all — That is a no-start fault and a different page.
Causes, most likely first on a Maytag microwave
- Failed magnetron — Ranked first here: a unit mounted over a range runs hotter than a countertop one, and that heat shortens magnetron life on this platform.
- Failed high-voltage diode or capacitor — Ranked second: a conventional transformer supply has a diode and a capacitor that fail audibly, which is why a loud buzz with no heat is so recognisable on this platform.
- Door interlock switch out of sequence — Last on this list: these units stack several interlock switches in series, so one failed switch kills the heating side while the light, the fan and the turntable all carry on normally.
Check in this order, and why
- Confirm the turntable, light and fan all work normally — Everything working except heat points at the high-voltage side. First: likeliest cause, least effort.
- Note whether the noise changed when the heating stopped — A new buzz with lost heat is diagnostic. Second: it separates the next two causes.
- Close the door firmly and listen for the interlocks clicking — A weak or missing click is the clue. Third: only once the checks above are clean.
What an owner can safely check
- Heat a mug of water for a timed minute and check the temperature — Cold water after a full-power minute is a clear result.
Tools: mug of waterAbout 10 min
- Note the sound the appliance makes, then unplug it — Do not open the case: the capacitor holds a charge.
Tools: noneAbout 5 min
- Close the door firmly and listen for a positive click as it latches — Do not tape or defeat a switch to test it.
Tools: noneAbout 5 min
- STOP HERE if the next step needs a meter on live terminals — That is where an owner check ends and a service call begins.
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off.
When to call a technician
Call once the power, the door and the cycle settings are all cleared, because everything beyond that is behind a case with a charged capacitor inside it. Call immediately if you see arcing inside the cavity, smell burning, or the appliance trips its breaker — stop using it and unplug it.
Nearest pages of this class
What this page does not cover
This page covers Maytag microwaves as a class, not one family or model line. It reasons from how Maytag builds this appliance — enough to rank the causes, not enough for wiring colours, torque figures or part numbers, which differ by family. Where a model-specific page exists it is linked here and is the better answer; this class page has no such child yet, so nothing is withheld by omission.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
