Loss of AC/Heater vent control
 

I've lost control of my heater/ac vents. The air flow is stuck on windshield defrost. The temperature control works fine as does the blower speed control. I just can't get heat to deflect to the floor or a/c to come out the dash vents. This condition started intermittently and has now become permanent. It seemed to start soon after my dealership replaced the cabin filter.