My car has a dial so you can direct the airflow from the ac/heater through vents around my legs, or through the dash, or up against the window. There’s also a button to control of the air input – one position brings outside air into the unit, and the other position recirculates the air in the passenger compartment. In the latter position, you can heat or chill the air quite a bit faster than in the former.
So why is it that the recirculate button is disabled when the airflow is directed against the windshield? So on really cold days like now, if I don’t direct the flow against windshield it starts fogging up. Which means I have to stop recirculating the air, put the flow against the windshield, and the car stays cold for considerably longer.
What’s the deal?