HVAC vent controls
 

I'm sure this has been answered a bazillion times, anyways I just charged the AC today. My knob that controls the direction of the airflow only works on two settings.... Off and Defrost/Floor. I looked at the control itself, it looks fine. I'm thinking it's a vaccuum that has to do with the control of the door. Where do I access this from to check? And where will run from the engine?

And the Blend door is what controls the flow of air to different vents, right? Mine could be broken but I don't know where/how to look. Thanks!

I ran in 3 cans and it's still not getting super cold, so I'm hoping to get this vent thing figured out so the semi-cold air will blow on me instead of keeping my windsheild cool