Why does my air conditioner make a pinging noise or drip water from the back?

A pinging noise is normal and is caused by water being picked up by the condenser on rainy days or in highly humid conditions — this feature is designed to help remove moisture and improve cooling efficiency. Water dripping from the rear of the unit is also normal, as water collected in the base pan during high humidity or rain can overflow and drip from the back. These are not signs of a malfunction. (Page 19)