An apparatus and method for cleaning split system air conditioning units. The apparatus comprises a shield functioning as a moisture barrier that sits between the wall and the AC unit and which releasably receives a drain pan that interconnects with the bottom of the shield to form a water tight seal. A flexible tube connects the bottom of the drain pan to a collection receptacle. Water and chemical sprayed into the unit to clean the unit drain through the unit, into the drain pan, through the tubing, and are collected by and can be disposed of from the receptacle. After the AC unit is cleaned, the drain pan, tubing and collection receptacle are removed leaving the area clean and dry. Kits comprising the apparatus of the invention can be sold together with new AC units or purchased separately.