Air conditioning not blowing thru vents only floor

We'll do this in steps,

First you must locate the vacuum switch, it will be on the firewall of the vehicle (the part that divides the engine compartment from the passenger compartment)
Once you find this check to see if all of the vacuum hoses are connected. If there is a nipple without a hose on it that is your problem. If that isn't the problem, check the vacuum hoses all the way to the motor. Look for kinks and Cracks. If you still have no luck, I would say you check the switch. The one in the dash. If you still have no luck post on here and we'll discuss further plans.