Yeah this Tankard fellas, Yo yo . Sorry i'm not going to be much help, but on my 94 GMC Sonoma, it kind of does the same thing your talking about. After driving it for a while, the blower sounds like it's blowing, but the air does'nt come out of the vents near as good as it should. I've never figured out this problem. Mine works fine when you first start driving it, but after 30 minutes or so, it does what you said yours does. They are different vehicles, but it's probably the same problem, which i have no idea what it is.