While riding in one of my best friends Sentra SE one cold night, he had the A/C button on while blasting the heat and I turned it off for him. I told him it was bad for his car. And he said it needed to be on or else it would just blow the cold air from outside. I continue telling him that it only does that if you leave the temp setting on cold and leave the vents open (recirculation button off). After some stubbornness, I ask to do a little experiment and try it with both the AC on and off, and he realized it still blew hot air with the AC off. He tried to argue it felt slightly hotter with the AC button off, but I just thought it felt more humid and still the same temperature.

So who's right in this situation? I've heard it's bad to blare hot air with AC on, maybe cause of the freon? Anyways, help me resolve this debate

 

It's not bad for his car. The AC turns on when you use the defrost setting, and that most certainly uses heat and AC at the same time.

 

AC also dries the air, keeps windows from fogging up.

 

AC - air conditioner - conditions air by removing moisture - it can be run hot or cold - no ill effects.

 

It doesn't hurt the car, though it may just be wasting gas if he's not trying to defog his windows. Both of my cars automatically turn on the A/C if I set it to defrost as does my wife's car.

 

Wow, quick responses. Thanks

 

it is, however, a parasitic load on the engine and may hurt its performance. But no actual "ill" effects. The heater uses the "heater core" which has hot coolant run through it so it can heat the air. The AC uses orifices, freon, etc, which cool the air.

 

Basically, I agree with what everyone else said. Having the ac on and the heat on high will blow hot dry air. Without the ac on, the air will be more humid. In the northeast where I'm from, the air is already pretty dry in the winter time. It may be different where you are located.