I have had this problem on my 95 Sonam, my brothers 99 Sierra and now our 99 GP is doing it. When you put the temperature all the way to hot and put it on the floor it comes out luke warm. When you put it on the dash vents, its hot. Put it on the setting for both dash and floor and you get hot on the dash and luke warm (if that) on your feet. Is this just common lately on GM vehicles, or what?