I have the Pull For Heat, Fan Speed which are self explanatory but what does the Temperature Control knob do and how does it do it? We had a freaky 70 degree day here in OH yesterday and today it's in the 30's. But one of the reasons I sold my Mustang and got the Bronco was to drive year round! Where exactly should I feel the heat blowing from? Is there a switch for Defrost? Thanks everyone -Jeff