Auto Climate Control Help

[Jacob_S1418]

I have a 2003 Silverado 1500 LT with the automatic climate control and I am having some problems. I have read many other articles about this but I can't find one that matches my problem so I decided to make my own post. Basically what's going on is when I set my climate control on auto the fan blows on the highest setting no matter what temperature I put it on and it just stays blowing on the highest fan setting no matter how long I leave it on. If I take it off of auto I can control the fan manually and it works fine. Also it only seems to blow super cold or super hot air, there is no in between temperature no matter what I set the dials too. I just got the truck so I don't know if the battery was recently changed or went dead because I know that that can cause problems. It's probably some actuator but I don't know which one or how to check if they are bad. Any help would be great, thanks.