The air conditioning on my 99 XJ is stuck on defrost. I am in the process of removing the dash, but it is not an easy job. If anyone else has experienced this same problem advice would be great!

 

Look under the hood. The HVAC sticks on defrost when the door does not get any vacuum

 

The arrow in the image attached points to air line that goes all the way to the air chamber (Black ball in front passenger bumper). I checked it for leaks but didnt find anything. Am I looking at the wrong thing?

 

You have a vacuum leak somewhere...the plastic line going to the black ball vacuum reservoir often deteriorates...check it thoroughly for cracks and holes. Also check the reservoir itself for cracks.