200 e-250 a.c. vacuum control problem

Thats suposed to be year 2000 above. My AC switch will not divert cold air to the normal front ducts. It only blows out of the defrost by the windsheild, is this a broken vacuum line or some other kind of problem. I checked the vacuum line under the dash in the passenger side where looks like it pulls the diverter down and there is no vacuum at that point. Where should I start looking next Thanks

Start by looking at all the vacuum lines coming off the intake manifold into a common block. If the vacuum line is off of the blend door motor it will go to defrost by default. This is a safety guard thing as the defroster in the winter time is the most important function of your HEAC controls. Listen for the characteristic whistle of a loose vacuum line. Most likely one has come loose or is cracked not allowing for a good vacuum pull to the blend door.