I was called to a home to clean an evaporator coil. The evaporator coil is the part of the air conditioner that cools the air before it enters the vents. The coil was covered in dirt and debris, which was causing the air conditioner to not work properly. I used a special vacuum cleaner to remove all of the dirt and debris from the coil. After the coil was clean, the air conditioner started working properly again.