ACC Unit Problems on 2007 9-3
 

I'm having some problems with my ACC unit on my 2007 9-3.
it seems like if I have recirculate on, the full fan power is working normally, but the minute I switch to regular, or auto, it knocks the power down significantly, and kind of makes a different noise.
It still seems to be slowing heat, just not like it used to (or like it does on recirculate)

Ive read things about calibrating the system...should i do that? Where will my fault codes show up? Do i even need to do this?

What could be causing this?

any help is much appreciated guys!

C