Disconnect the power supply to the microwave from the wall outlet.
Slide the grease filter on the bottom of the microwave, then press down on the tab.
Pull the grease filter out to gain access to the vent fan.
Inspect the vent fan for any cracks or broken pieces, using a flashlight if necessary.
Remove the four screws holding the bottom panel in place, using a screwdriver, if you need to remove the fan.
Use a wrench to loosen and remove the bolt attached to the mounting plate that keeps the fan in place.
Remove the fan from the unit. Replace the fan if needed, then reinsert the mounting bolt.
Reattach the bottom panel and reinsert the four screws. Clean the grease filter, if necessary, using soap and warm water.
Slide the grease filter back into place, then reconnect the power supply.