I have researched your problem. The vent doors are cable operated. You may have one disconnected, looses, broken, something blocking the vent door.
I have attached the trouble shooting directions from Mazda for your review. As far a diagnosos without removing the dash, you should be able to hear the vent doors open and close. The air flow door cables / wiring will be both in and outside the system.
Saturday, January 29th, 2011 AT 6:16 PM