You're missing the whole point. The dial is only for the face vents. If its zero outside (okay 32 for your Fahrenheiters) and you want it 23 (74) in the car its going to blow hot air out of the vents so to prevent you getting a hot blast into your face they give you a dial so that you can adjust how hot the air is coming out of the vent. It doesn't blow cold air out if its set to cold so that they are working against each other it just restricts the amount of hot air so that the car doesn't warm up through your face.

It's brilliant engineering