The first thing you need to replace is your a/c service company. Try to replace them with one that knows what they are doing. If the first "pump and pan" didn't solve the problem, why did they think a second and third would. No one is going to be able to diagnose your problem without seeing it, or at least having a lot more information. Not flamin ya, but your post is like asking "My car won't start. I have replaced the ignition switch 3 times. What could be the matter with it?" Does it leak al the time it is running, or does it seem to go ok for a while, then lets loose with a bunch of water? About all you can do yourself at this time (and the same place a pro would start also) is to look at it when it is leaking, pinpoint exactly where it is coming from, then you can find out why it is coming from there. Of course there are two problems trying to track leaks down: they won't leak when you are watching, and the source of the leak is not always directly above where it comes through the ceiling -- it can drip onto a board or something else and run several feet before finally dripping down to the ceiling.If you need more help, post more info, and you will get more replies. Good luck Larry