2000 Pontiac Grand Prix AC Heater Climate Control

I'm having a problem with the external temperature reading high. I've taken it in and had the ambient temp sensor replaced with no change. I've taken it to the GM dealership and they said it needed a new HVAC control head (#10435239 ). I purchased a brand new one on Ebay and had the mechanic at goodyear install it today. The temp is still reading high and the car starts to blow cool air before the inside gets up to the temp I have set. When I was driving home today from goodyear the temp outside was reading 47F, but the actual temp was 26F. When the car is in the garage and I go to start it in the morning it reads 75F when it is 12F in the garage. Could I have a bad sensor?