Hyundai Repair: a/c vents, climate control system, model vehicle

Question
a/c blows cold but will not change from defroster vents to dash vents

Answer
Depending on the climate control system you have, this will most likely be a problem with the cable between the climate control head and the heater box or with an actuator or lever on the heater box.  If you need additional assistance, answers to the following questions will help me properly guide you.

What year and model vehicle do you have?
Do you have automatic or manual climate control?