Ford Repair: 2003 Ford Ranger Dash Vents, vacuum tank, vacuum source

Question
I have a 2003 Ford Ranger and my dash vents have stopped working.  The AC comes out of the defrost vents.  I bought a book by Haynes to look up the problem but they don't show or talk about this type of problem.  Also, this problem could be caused by rodents that make nests inside my engine and chew on some of the tubing.  I've crawled under the truck but I can't find anything loose or missing parts and I can't see anything while looking inside the engine.  So, I need some help.  Where do I look and what am I looking for.  Thank you

Answer
look for a vacuum hose coming into the truck from the engine compartment
usually on passenger side it may be going into the wiring harness leading into the truck could be white or black small plastic tubing.
check and see if it is chewed or crumbly it should be going to a vacuum source on the engine or to a vacuum tank.