13,5K BTU vs. 15K BTU?

Another thought....if the problem is that your A/C units are freezing up, the above suggestions are very valid...cleaning, sealing, etc. But, you might also have a misplaced or bad freeze sensor. My 15K unit on the front kept freezing up and what I found was that the freeze sensor had fallen off the coil. After finding that last year, I put it back into place and resealed all the inside of the unit where the cold air was getting back into the air flow across the coils..... And, as of this morning at 80 degrees outside with about 85% humidity, (so thick you can cut the air with a knife)... it was a very comfy 70 degrees inside!