i have 2003 suburban, since i changed my battery, my ac damper bumps and bangs but refuses to let air out the front vents. it re-routes air back up through defrost, any suggestions

You may have to reprogram or reset it.
I do not have much info on a 03.
But here is a good AC link that can help.
http://www.autoacforum.com/
Or someone else may be able to help.
If not. For fast instant help in about 10 minutes.
There is always the All Data DIT repair info sub. Good info 24.95$ a year
online sub.
http://www.alldata.com/products/diy/index.html
Good luck MT