My AC on my 99 XJ works fine however when turning on it's always doesn't blow at full speed and after a few minutes of running, I hear what sounds like a door open then it blows at full speed. Any ideas of what's wrong ?

 

vacuum leak.
Check my thread, I dealt with this recently.

 

I agree. Does the blend door open better when the engine is running faster/under load?

 

Yes. Is this hard to fix ?

 

So I have an issue similar to this...

My AC blows real hard and cold when its not under much load, but when I start going up hills itll only blow out of the defroster, then when not under much load again itll start blasting from all the vents. Any ideas?

 

I would say your vacuum canister is gone? Mine did same thing until I put a new vacuum canister in.

 

This an expensive issue to fix ?

 

look under hood at vacuum line for small crack or hole also check vacuum storage can behind front bumper pass side

 

What do you mean "gone"? Is this a pricey fix?

 

no hit junk yard every vechicle has them if a xj cant be located search for similar size else where in the yard

 

Where are these on the vehicle? I'm not sure I even know what you're talking about.

 

its a small black bottle located usually behind the front right corner of the bumper. has one vacuum hose going to it