In my case, all the vacuum lines under the hood are in good condition, and the vacuum tank hold preasure now!
My problem is with either the controller, or a vacuum line under the dash.
I used a rubber vacuum plug and plugged the AC vacuum port under the hood, now the vacuum line holds a steady 17 In Lbs.............
In the interum, I ran another vacuum line from a spare vacuum port on the manifold (drivers side), thru the drivers fender, thru the large rubber gasket for the door electrical stuff. Then I removed the vacuum line to the actuator above the gas petal, and voila, the AC now goes to the dash vents.
Note, I added an inline shut-off valve (i.e. used on fish tanks) so if i needed to switch back to defrost, all I needed to do was to close the valve.
This now allows me to use the jeep, and give me time as to find the real problem in the dash board!