Microwave ovens have light bulbs installed in one or two locations, depending on the microwave's design. Almost all microwaves have a light that illuminates whenever the door is opened or the microwave is in use. Microwaves designed to be installed over a range or cooktop also have a light on the bottom of the unit, which is designed to illuminate the surface below. Eventually, the light bulb in your microwave will burn out and must be replaced.
Surface Light Replacement
Unplug the microwave. Often, the microwave will be plugged into an outlet installed in a cabinet above the microwave.
Remove the screw from the side of the light cover, located on the bottom of the microwave, then lower the light cover. Often, the light cover will be connected with a hinge and will not separate from the microwave.
Depending on the model, you will have to unscrew or pull out the light bulb.
Thread a new light bulb into the light socket, or if installing a halogen bulb, push the bulb into the socket. If installing a halogen bulb, wear gloves before handling the light bulb because the oils from your fingers can damage the bulb.
Replace the light cover and secure it with the screw.
Oven Light Replacement
Unplug the microwave.
Remove the two screws on the grill above the microwave door and remove the grill.
Find the light fixture inside the upper cavity of the microwave.
Remove the light cover with a screwdriver, if necessary.
Unscrew the light bulb to remove it.
Install a new light bulb by threading it into the light socket.
Replace the light cover, then replace the grill and secure it using the two screws.