You've probably got two issues you need to deal with. Overheating is caused by NOT having a vent to the outside. Air Conditioners are simply heat transfer units. That is they take the heat inside and send it outside. Thus making the inside cool.
The other is in that process moisture condenses on the "evaporator", part of the A/C unit. That moisture has to go someplace. If you don't provide a drain it collects on the floor and eventually you'll have a rotted out floor.
Byron & Anne enjoying the everyday Saturday thing.