Marlboro27s

maybe this is an easy question, but ive been hearing different answers for my entire life, and im still not sure.

when you gotta defrost your windows due to all that vapor and shit...do you put the defroster on hot or cold. I think its hot, but sometimes hot doesnt work, while cold does. but then i use hot and that works better....so what the fuck is it??

some people tell me cold, some tell my hot. i tried today and hot didnt work at first, but after like 10 minutes it finally started to defrost....so what the hell??

someone explain this to me

1killercls

Another post pointing out the far superior American Education system.

dallison

as long as the ac compressor kicks on, either one should be fine. in the winter hot usually works the best. in warmer weather either one, your choice

GIBSON6594

if there is ice, hot, if not, cold

95gt

Maybe it worked after 10 minutes because the car warmed up and actually started blowing hot air

1killercls

see my above post.

95gt

I know.


I think this question is better than your joke thread. 9/10

NSXNEXT

iTrader: (2)

www.howstuffworks.com

Shoofin

danny25

more important than the temp is using outside air at the same humidity level, and the AC helps too. That's why on the CL when you put the defroster button it automatically turns off the recirculating air and turns on the AC

optiq

i'd say cold air

TSX Hokie

A quick lesson in Psychrometry:

Warm air can 'hold' more water vapor than cold air. For a given humidity, temperature, and pressure, the air can be quantified by its dew point, the temperature at which the air/water solution becomes saturated and water starts to condense out of the solution. Dry air has a lower dew point than humid air, which is why dew forms overnight in the summer in New York and not in New Mexico.

In your car, a few minutes after starting your car in winter, the windshield is still cold but the air in the cabin has warmed up, and it has become more humid because humans release water vapor when breathing/sweating. Thus, water condenses on the windshield because the air temperature near the windshield is lowered below its dew point.

How do we prevent this from happening? Turning on the air conditioner lowers the cabin air temperature below its dew point inside the condenser unit of your A/C, thus lowering the dewpoint, and water that would have condensed on your windshield condenses inside the A/C instead and drains away. HOWEVER, if you heat the windshield, it will no longer cool the air below its dew point. It does take a while to warm the windshield up this much though.

Thus, the fastest way to defrost the windshield is to blow hot air on the windshield but air condition (cool) the rest of the cabin air. I'm not sure that most cars' HVAC systems are capable of doing this, so doing either alone would have the same effect, albeit slower.

EDIT: Danny is right, turn recirculation off, because if you are recirculating, you are just allowing the same volume of air to get more and more humid as you breathe into it.