Heat element not working

The problem is the magnetron, "heart of the microwave oven" or the inverter board if 7 years old or less.

Heating element problem.Either element is cracked or its connections are loose.You will have to heck with meter, to confirm, whether its element or its shorted wire to the elements.---------Thanks.

That would be a faulty magnetron if it dos not heat. It should have 1 year manufacture's warrant and a 30 day store warranty.

Sadly your microwave has done it's last cooking. The mechanism you need to make it cook again would cost you more than a replacement microwave.

Sounds like you have a thermal reset opening up on the unit and disabling it till it cools down. Make sure all air intakes are clear of debris, papers from the counter , etc. also make sure no dust covering air intake holes. Do you hear a fan running when the unit starts?? If not, bad fan, burnt wires. bad main board. Like a lot of my other posts, maybe a bad fuse and fuse holder. Check for brown flux coming out of shiney metal end of fuse, where it meats the ceramic body. Replace fuse and fuse holder. Sometimes fuses do just get tired and barely open, not actually blow, then just expansion and contraction of the element inside will make the unit work and then quickly shut off. Cheapest way is just sub the fuse and give it a try. Cost you a dollar or two, if that works replace the fuse holder too.

most likely the power supply in the microwave is gone. the microwave die probably it is over the oven. heat from the stove cause the microwave to heat up and cold off more than it is on the counter.
counter microwave has fan and air slot in the rear. it keep the motor and microwave cool, and there nothing else to keep it hot. but the over the oven, the only ventalation is from the top. and with the added heat from the stove top and oven.

SOUNDS LIKE THE MAGNETRON WENT BAD IT'S ABOUT A 100 AND SOME DOLLAR PART

The most common problem would be your magnetron. Check your purchase date, magnetron's usually have a five year warranty. Not a part I recomend trying to fix yourself (high voltage ).

My magnatron went out on my 2003 model ge replaced the part but I had to pay the labor.Mine had a ten year warranty on parts.