When your air conditioning system is running, you’ll occasionally hear the sound of dripping water coming from the indoor cabinet. This is normal. You’re hearing condensate from the evaporator coil falling from the coil down into a pan.
The reason water develops in an air conditioner is because of the evaporation of cold refrigerant along the indoor evaporator coil. The process of evaporation removes heat from the air to cool it. But as a side-effect, the evaporation also causes moisture in the air to condense in droplets along the coil’s surface. Below the coil is a shallow pan—the condensate pan—which catches the water. A motorized pump then removes the water out a condensate drain and outdoors where it’s deposited on the ground.