Why would your window air conditioner develop ice on the front coils?

im a appliance delivery and repairman and the air condition is probably sitting too level or leaning forward and the condensation that builds from the coils being cold in the hot outside air cant run out the back of the drip pan on the bottom of a/c unit, so try tilting it back if that dont work the holes or seam crack could be clogged , and if all that fails then your regulator is putting out too much freon and your better off to purchase a new on and pay for the professional install and when they install it put a level on it and make sure it is leang toward the ground on the outside of window!