Chevy & GMC Vans

I'm pretty sure vac lines are ok. I already fixed the blowing only on the defrost vent months ago.

Now, no matter where I have the vent setting, it comes out all over the place. defrost, dash vents and floor.... at the same time

the amount does change, for example, if on the defrost setting I feel it from the dash vent, then if I move the switch to the dash vent.. more comes out of them but it still has some coming out the defrost.
this is exactly the same regardless of which setting I'm not... it's liek it doesn't fully shut one off before moving to the next setting...

ideas? thanks
Rob

On the passenger side, up under the dash is an "air box" or plenum. There are dampers inside controlled by vacuum motors which you can watch operate, with the van running, after some minor disassembly. This is easy to get to from inside the van.
could be a bad vacuum hose up under the dash or a bad vacuum motor. Also, it could be something came loose inside and has blocked one of the dampers open.
As far as an issue with the dash switches themselves, someone else will chime in I'm sure.

cool info kings. i'll have to check it out.

hmm.. probably totally unrelated to the hissing sound I hear on the drivers side after I accelerate hard and let off then I hear a hiss for a second or two...

If you had vacuum boost brakes, I'd say check the booster. If it were a booster leak though, you'd probably notice a change in the idle when you applied the brake. If you have hydro-boost brakes then my thoughts are moot.

hmm.. ok .. reallllllllllll stupid question.. how do i know which brakes i have? ..

If it was a vacuum booster, you'd be able to see it no problem. Sits right between the master cylinder and the firewall.
Just noticed your avatar - funny!