A/C Vent Problem

I recently purchased a 99 Cherokee Sport. The A/C control is not working properly. It seems the air always wants to go through the defroster no matter what the knob is turned to. Sometimes it will come out through the other vents for a short time but eventually it circulates back through the defroster. It sounds like the vents aren't opening / closing correctly. I've heard this might be some kind of vacuum leak. Has anyone else had this issue? How did you fix the problem? I previously owned another 99 Cherokee Sport and had the exact same problem but never bothered to fix it. Thanks for your help.

search for vacuum canister. It is the one in your bumper, that is the prob.

More specifically, your problem is caused by low vacuum. That is caused by a leak in the vacuum system. It can be the canister or any one of a number of vacuum lines. It can even be caused by a bad vacuum brake booster or loose intake manifold bolts. Normally it is a pretty straight forward task to track it down.

Hmmmmmm.... I had the same problem. I assumed it was a broken cable in my case, I did realize the vents were vacuum actuated. Still a newbie to the Cherokee, which is quite different from my FJ55.