Best way to seal off the rear of an air conditoner to prevent dirt and bugs from entering?
You cannot seal the condensing coils. The back is where the heat exchange occurs that allows your AC unit to get rid of the excess heat. You can add a external screen or filter media to reduce dust &amp; bug buildup but this will require regular cleaning. If your system has an vent option to bring in outside air only a small amount of outside air is brought in through the evaporator coil and cooled. Window units should have a slight tilt down in the back to make sure the condensate can drip out the back of the unit this is normal. The slight tilt allows the condensate to drip out the back and any rain water that is on the unit to drain and not enter the home.