Kenmore microwave Model No. 721.62463201 runs but does not heat and has a terrificately loud buzz. All lights displays are normal

This is normal. Kenmore microwaves will stay running with fan and light on for a short time after food is cooked. The reason is to air out the microwave after cooking. Things like pop corn, Bacon etc. have strong smells after cooking. The ventilation helps to remove odors.

Whirlpool Microwave Buzzing Loudly - ApplianceBlog

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Aug 12, 2011 - 10 posts - ‎2 authors
My Whirlpool MT4155SPS-2 microwave oven has recently started to buzz loudlywhen operated. The sound is getting louder and more frequent ...

Whirlpool making intermittent loud buzzing noise Microwave ...

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Whirlpool microwave ovens making intermittent loud buzzing noise related questions and answers. Ask your ... ...loud buzzing noise and it doesn't heat. i just tried it again and let it run for 1 minute. ... Question about Accuwave Microwave Oven.

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If your microwave buzzes loudly and produces no heat you probably have a defective power .... I have a whirlpool oven range and it's less than a year old. .... Humming sound stops when I open door to remove food, but when door is closed, ...

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Usually that is a sign that your magnetron tube has gone bad (shorted out).

If you need further help, reach me via phone at https://www.6ya.com/expert/ronald_e6b9572cebe3ad27

see this causes and fix it. God bless you
Magnetron If the microwave is loud or noisy only when cooking, the magnetron tube might be defective. The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. Under normal circumstances the magnetron is nearly silent. However if it is damaged or nearly burned out it can begin emitting high pitched or growling noises. It's not normally dangerous to use a microwave oven when it makes these noises, but they are an indication that the magnetron is almost dead and will need to be replaced.
Exhaust Fan Motor If the microwave is loud when running the fan motor might be
Stirrer Motor If the microwave is loud or noisy the stirrer motor might be worn out. The stirrer is a metal blade which slowly turns around, deflecting the microwave energy in a random pattern inside the microwave oven. As the motor nears the end of its useful life it begins to make grinding noises. The microwave will not heat food evenly without this stirrer, the motor should be replaced.
Turntable Motor If the microwave is loud or noisy the turntable motor might be worn out. This is a common problem and relatively easy to replace.

This is a strong indicator the magnetron is fried, also! this is the most expensive part to replace in the microwave oven, and in most cases cheaper to replace the whole unit.

Hello there:
There's no heat, When the microwave won't heat, soemtimes you will get a loud buzz, you usually have a defective power diode, high-voltage capacitor, or magnetron. We recommend that you consult with a qualified appliance repair technician for help in determining the problem and deciding what to do about it.

The loud buzzing you hear is the sound of the magnatron tube.That is what emits the microwave radiation and buzzing should be normal. The mag tube may be nearing its end at witch time you will hear no buzzing and hence no heating of foods. Replacement can be costly depending on the model so most people just opt for a new one. Hope this helps

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

Q - The microwave display counts down and the inside light is on,  but nothing is heating and the fan is not running.
A - This most commonly is a bad door switch, other possible problems are a faulty relay or solder joint on the power module, but a bad door switch is most common.
 Q - My microwave is running and sounds like it is working but will not heat up anything.
A - Many thing can do this but, common things are....loose high voltage wire.....poor solder joint on board.....magnetron.....power relay.....
Q - The microwave makes a loud "hum or buzz" noise but will not heat up the food?
A - 9 times out of 10 this is usually this is a bad magnetron, the other time is sometimes a bad high voltage diode. See components section.

Have you tried putting a cup of water in it and cooking on a low power level? If it buzzes only when it is on the cook cycle, that would narrow it down. More detals might help us help you, including the model number.