Okay here is the situation. On my 97XJ I am having air only blow out of the defrost on the dash. I have found that this is likely a vacuum leak. However, here is the interesting part. It has just started getting warm here in W. Mass and I tried the Air-Con settings. Air Conditioned air will blow out (dash only) when any of the air condition setting are selected, as well as the defrost setting, and the defrost with feet setting, not the face or feet only settings. My question is, does this sound more like a problem with the ventilation unit itself and that should be replaced? I have traced all the vacuum lines and found no obvious problems (hoses not connected). Let me know what you guys think about this and thanks for the help!

 

I have a similar problem and have just been ignoring it, but hopefully someone has a fix!

 

It could be two things. Your selector in the dash or you might have a hole in one of the vacuum motors. Personally I would lean towards the vacuum motors.