Is there a chance the drain on the bottom of the AC that drains onto the roof is plugged some or totally? We have had this problem in the past so I went on the roof and found the drain. It is in the door side front corner. It is about 3/4" in diameter and grayish white. The hole in it is only about 1/8" in diameter. I cut it off about 1/4" and the now the drain hole is about 1/2". It was plugged up with some snotty looking stuff. AS soon as I cut it off water started pouring out. Something for you to check and think about.