My heater doesn't seem to get hot. The AC works fine, but when I switch to heat it doesn't warm up. The temp gauge works, the hoses to the heater core are both warm. I took the cover off the heater core and there is hot air coming out the bottom of the cover. It doesn't seem to blow much air when I switch to defroster either. Any ideas? No matter where I set the knob (floor, vent, or defroster) I don't get hot air. I checked the knob for the heat control and it seems to be working properly.