Micro wave not heating

usually when you kill the power and then when you put power back on the machine works it's the computer board that's bad.all you're doing is resetting the board just like your house computer,if something happens to it you shut it down and reboot it,that's what you're doing with the micro wave just rebooting the board.here's the funny thing about micro waves sometimes the part you're gonna change is almost the same price as a new micro wave so i would first check how much the board is,i went on sears and they have the board for 115.00 repair clinic for 235 part number WPW10216347 they don't make this model anymore but you can get a stainless micro for around 290 to 300 dollars and if you buy the same brand all you should have to do is remove the bolts up above that hold it in place and remove the micro wave and the same brand should mount the same way so you won't have to drill new holes or replace the back metal panel.if i were you i would replace the unit instead of the board repair clinic shows most of the parts for this model out of stock so it might be a while before you can get any parts for this model but this is up to you.good luck with your micro wave.one more thing when you were in there did you see alot of grease,this is usually the cause of no heat,the grease from cooking on the stove top gets into the micro wave and on the mag tube and damages it,if there was grease in there i would just replace the unit

Replace the door interlockswitches - or try re-positioning the existing set. They wear after time

Micro wave as the name suggests produces heat when the micro waves aimed at an object causes the water molecules inside the object to vibrate hence producing heat.The gadget responsible is the magnetron. If your magnetron is not receiving ht voltage or receiving but faulty, then your micro wave wont work please take precaution when opening micro wave due to high voltage caps that remain charged sometimes even when it is off.check the high voltage fuse/ diode and capacitor if they are fine and the step up trans former o.k then the only option is to replace the magnetron

Check the door safety interlock switches. Magnatrons are pretty tough but the little switches are not.

FIK IT THE HEATING ELEMENT IS STRIGHT FORWORD AND COST IS CHEAP, GO FOR IT .

Replace the HV capacitor

The light inside the micro wave needs to be replaced most have a door on the back side that yo can remove the screw and unscrew the bulb and take to a applince shop and purchance a new one to replace.

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.

In the case of microwave ovens, the commonly used radio wave frequency is roughly 2,500 megahertz (2.5 gigahertz). Radio waves in this frequency range have an interesting property: they are absorbed by water, fats and sugars. When they are absorbed they are converted directly into atomic motion -- heat

So, NO Micro waves NO heat......... Need to check for Microwave emitter device installed inside.

This just happened to ours as well. Apparently the magnetron (device that creates radio waves that heat the food) is broken. I'm trying to pry the darn thing out of our kitchen now so I can replace the magnetron. Look for this part WB27X10489 on Google. I found it on ebay for $65. If it fixes the problem I'll post again.