When I turn the heat on in my 97 GTP, the passenger side blows hot air but the driver side blows cold air, whether it's defrost, vents, whatever. I noticed in the summer that on long trips, like 6 hours, the A/C would not be as cold after a few hours....Any suggestions on what the problem might be?? It's sort of cold here in Pittsburgh at the moment and the heat not working on my side is getting old lol......Thanks