96 Silverado A C Control head unit ?

I had a problem w/ stereo ,worked on it and re installed unit.
When i put it all back I must have did something cause now all my AIR blows to floor.
Any thoughts before I take it apart again would be great.

that is controlled by engine vacuum. Vac line gos from top of engine manifold throw the passenger side fire wall to control head. make shue you have no leaks in that vac supply hose. That can cause you problem

Thanks, i fixed it,the actuator located to right and above gas pedal had gotten knocked off center. Works great after re bolting it back in place.
Another issue for the life of that truck each time you take a corner over uneven ground where rear end flexs there is a popping noise under rear.
Sounds like the axle shifting .any thoughts.