AC Problem with my 2000 Mustang?

I believe that the yellow vacuum hose you are talking about is the main one leading from the vacuum ball located inside of the right front fender closest to the door and it leads to the heat and air controls or to a silver vacuum modulator under the dash. Either way you should be able to get at it without taking the dash apart. But like the other gentleman said you have to lay with your head under the dash and your legs hanging over the top of the passenger seat and once you extend the hose, if it doesn't reach the A/C panel then it has to go to the vacuum modulator located in the dash on the passenger side.