Hi , im having a problem with my air vents , when i put it on front vents it starts to sound funny and the air starts to sound like its blocked and it is , stops coming out of the front vents and just has difficult time switching between any different options , like floor defrost and both combined ???????

my 99 cherokee sport is not lifted but restored

 

You probably have a vacuum leak somewhere. Check on the passenger side right behind your front bumper, you'll see a black spherical canister. That's your vacuum reservoir. Check it for loose connections or deteriorated lines. If that ball isn't working, neither will your airvents (or cruise control, if equipped).

 

What pocketsempty said. Also there is a check valve off of the back of the intake manifold for vacuum. Check that. Blow in it on both side, air should only pass 1 direction.

Also could be your actual a/c panel, bad connections on the back.

Or bad actuators. Under the dash and a pain in the @ss.