Pontiac Repair: 99 Pontiac Grand Prix A/C, grand prix gtp, pontiac grand prix gtp

Question
99 Pontiac Grand Prix GTP 3.8 supercharged. Car has dual auto a/c controls. A/c on drivers side noticebly warmer than passenger side no matter where temperature is set. Passengers side will get ice cold, drivers side just cool. Some kind of mixing valve? Where would it be located? Car has 37000 miles and though this problem is recent, I've always noticed strange noises coming from inside the dash, like valves opening and closing.  

Answer
You either have a blend door actuatorthat is not working correctly or your AC system has a low charge. The most probable cause is a low charge. When the AC system is low, the lower half of the evaporator core will get cold but the top half wont. The way that the ducts are setup uses the lower half to cool the passenger side and the top half to cool the drivers side.
The reason that I said that this is probably the cause is because you said that it doesn't matter what temp it is set on. Usually if it is a blend door problem, the temps will even out at some time and yours doesn't.
Have your AC system checked for leaks.