Day one my A/C was pumping 100% cold crisp air, the next day the car will only pump the hottest heat possible. It doesn't matter if I have it on 60 degrees or 90 degrees, A/C or heat; it just pumps the hottest air possible. I can turn everything off and on just fine, and I can change the direction of the heat (feet, dash, defrost), and I can control the intensity of the blower, just not the temp. What is the problem and how can I fix this??