A microwave consists of multiple components, and if any of these components break, it may cause some features of the microwave to stop working. If the microwave ceases to operate at all, it may be due to one small component: the fuse. The fuse of a microwave may burn out at any time, especially after years of use. When that happens, the microwave will stop running. Replacing the fuse will return the microwave to working order.
Unplug the microwave from the outlet. Open the door of the microwave and remove the turn plate.
Turn the microwave onto its front on a soft surface so that the back of the unit faces up. Remove any screws around the outside edges of the metal microwave back and pull the metal back off of the unit.
Follow the power cord to see where it enters the unit. The power cord generally ends at a boxed area of the unit, which contains several components, including the fuse.
Find the clear, cylindrical glass component that looks like a long light bulb. This is the microwave fuse. If the fuse is in working condition, it should be completely clear; a damaged fuse appears black or brown.