Just to continue the thread to the inside of the car....The heater knob, marked "H" controls the flapper valve at the inlet to the heater core. It is supposed to work as follows, push it in allows heat into the car, pull it out to close the flapper valve. When the flapper valve is open, turning the knob to the right turns on the squirrels and they produce heat. Why did the designers put a vent on the front? Too costly I guess.
Scott in CA