i have problems with my 97 chevy blazer with the ac blows on your feet and out the defrost. i have replaced the vaccum ball and vaccum lines. i have talked to many people and no one thinks that it can be the switch but i think it is.has anyone had this problem

 

It could be your switch?
I have delt with the NBS a/c controls yet, however on the old body style they were controlled by vacuum. Sounds like nothing has changed. All the switch does is take the vacuum and divert it to the proper door controls to move the air around in the vents.

I would check to make sure the doors are free moving, free of obstructions, before replacing that switch. It could also be as simple as a pinched vacuum line.

 

I have a 95 Blazer that has a simular problem but when I change to selector from one ac setting to a nother it blowes out in diferent places but still not where it belongs

 

That sounds like your vacuum harness connected to the back of the switch is on incorrectly, or a couple of the vacuum control lines are mixed up. Pull the switch and take a look.

 

I know this may sound stupid but first of all before you do anything else crack the hood open and look closely at the lines to see if any of them are leaking air (listen for a hissing) if you hear that clip the line about a inch and re-attach it. That was happening to my 97 blazer and it worked great after that.