Auto Air Conditioning & Heater Repair: Fan Outlet controls, ford ranger truck, air vent

Question
I have a 1997 Ford Ranger truck (2.3L) that I recently took to the shop to have its alternator checked.  The alternator was found to be bad, and after replacement I no longer had system charging alarms, and all seems to run great, but one thing that I did notice that was different was that I no longer had control over where my air conditioning and heating air would be directed.  The fan works, but all air now comes from out of the defrost vents at the base of the windshield.  I still have air conditioning, I still have heating, and I still have just normal ambient air should I choose to have that air circulated, but whereas before the alternator replacement I was able to choose & direct that air out of the front vents, or out of the vents that pointed towards the floor before, it will only come out of the vents at the base of the windshield now regardless of what air vent position I select with the fan / vents control dial.  My question is  "Is there anything that a mechanic might accidently  disturb, or could there be a fuse that could be blown while changing an alternator, or disconnecting a battery that might influence fan vent controls to a point that air will only be able to come out of the windshield defrost vents?"  Any information that you might be able to provide would be greatly appreciated. Thanks in advance for your help.

Thanks,
Mark

Answer
Hi Mark

On the passenger side of the engine compartment you will find a vacuum hose that is attached to the engine block.  The black one goes from engine to a tank by the fender well.  Another one will come out of the tank to the evaporator case (from the bottom) thru the fire-wall.  Check the the black hoses they may have come undone.