I have a 97 Cherokee and the only air that comes out is on the top vents, no matter where the selector is set. I found a vaccum line broken, it goes to a softball size something that is mounted to the inside of the front bumper. Anyone know what that is and if that maybe causing my problem?

 

The ball in the bumper is your vacuum reservoir,it has a check valve in it,when you accelerate your engine vacuum goes to the check valve.

I believe it could affect your air flow.

I know when I purchased my vehicle the previous owner had the ball backwards which made my vehicle gutless/underpowered and a semi could probably take off faster than me.

My air doesn't work so I don't know if it affected mine but seems reasonable to believe so

 

Mine was a rat nest blocking air flow