Defrost.

[Racer X-8]

Oh, by the way, when I was out there feeling the air coming out the defrost vents, that air was pretty darn hot. The engine was at normal operating temp and it's about 60 degrees here in SC, right BMGYaris?

Do you know that you don't get any heat in that air until the engine's thermostat opens? That's right. The engine holds its coolant inside of the engine until the temperature of that coolant in the engine gets warm enough to open the thermostat. That opening of the termostat lets the hot coolant circulate out of the engine and through the radiator and the heater core. The heater core is like a small radiator - it exchanges heat into the air that's blowing through it. That air that's blowing through it - that the hot coolant exchanges heat into - in the heater core - is what you are trying to use to defrost, defog, and also heat-up the interior of your car. So remember, the heater core doesn't get any hot coolant to heat the air - until the engine's thermostat opens and allows the heated-up coolant to go there.

[BMGYaris]

Originally Posted by Racer X-8

Oh, by the way, when I was out there feeling the air coming out the defrost vents, that air was pretty darn hot. The engine was at normal operating temp and it's about 60 degrees here in SC, right BMGYaris?

WELL today yes. BUT a few weeks ago it was about 10 degrees when factoring in wind chill factor. We have had several freezing days, and then the next day will be over 50, sometimes approaching 70. Crazy...but on those freezing days i did have to deal with ice:P