Fuses
Usually, when your microwave oven doesn't work it all, the internal fuse (thermal fuse) is blown. This fuse protects both you and the oven. When it blows, you need to have a qualified appliance repair technician replace it.

Door switch
If the fuse isn't the problem, check the door hooks and the door-release button. When these are broken, the door switch doesn't activate, so the oven can't work.

It sounds normal, but there's no heat
When the microwave sounds okay, but there's no heat, one of the internal door switches, the high voltage circuitry, or the circuit board may have a problem. To resolve this problem, you need the assistance of a qualified appliance repair technician.

I can't adjust the power level
When you can't adjust the power level, there's probably a defective triac (a type of electronic voltage control) or a problem on one of the circuit boards. You need to have a qualified appliance repair technician diagnose and repair your microwave.

The carousel won't turn
Although the carousel is usually driven by a small motor that's unrelated to the heating function of the microwave, the microwave cabinet needs to be opened to repair it. So we recommend that you seek the assistance of a qualified appliance repair technician. Inspect the plastic drive coupling that the tray sits on, as well as the ring-and-roller assembly, to make sure that they're working properly.

I have intermittent cooking problems
Many over-the-range microwave ovens suffer from intermittent problems caused by excessive moisture from the range/stove entering the microwave cabinet and collecting on the circuitry. Often the problem is with one or two simple connections that may need tightening or soldering. But, to repair these components, the microwave cabinet needs to be opened. So we recommend that you seek the assistance of a qualified appliance repair technician.

The display flickers
If the display flickers mildly and doesn't affect the way the microwave works, don't worry about it. However, if the flickering is severe and coincides with cooking problems, you need to pursue a solution. Because repairing this component requires opening of the microwave cabinet, we recommend that you seek the assistance of a qualified appliance repair technician.

There's no heat, but it buzzes loudly
When the microwave won't heat, but you hear 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.

It quit after I slammed the door
When you slammed the door, you may have blown a fuse. See It doesn't work at all.

It looks like there's lightning (arcing) inside my microwave When you see rcing inside your microwave, it's because of food or liquid left in the cavity or on the wave-guide cover:

If the wave guide has any burn spots, replace it and clean the unit well.

If the cavity has any burn spots, spot-sand it smooth and touch it up with microwave interior paint.