1997 Chevy S-10 No cold air blowing again

I had my ac system checked for leaks and charged with r-134 refridge.
AC worked well at all ranges both from lowest fan setting to the highest and from the coldest setting to the highest for about 4 day's and now there is no cold air blowing.
Tech assured me that he did not find no leaks and that presure was fine. We double checked fuses and conection to all possiable know points and all is well.
I was told by a co-worker that he had a simular problem with the ac in his car, which was a 1995 volvo. His problem turned out to be a blown fuse in the back of the interiour ac control knob. Now before I go ripping out my dash for any reason, do you know if this is true in my case? L