Defogging Windscreen

[Caesar]

Having a raging debate on this with my brother.

I have always assumed you crank the heat, because the heat causes the fog to evaporate off the windscreen. He says crank the cold, because cold air is drier and works as a dehumidifier.

Who's right?

 

[Footypie32]

Science has never been my strong suit, but I always thought the fogging was caused because the temperature on either side of the glass was different, ie: Outside is cold, inside is warm. I think you just have to get the glass to a consistent temperature. Or I could be completely wrong...

It certainly does piss you off though.

 

[Ripper]

Cranks the heat up with the A/C on. The A/C will dehumidify the air in the cab. Turn A/c off once windows are clear and turn it back on as needed.

 

[TheFreshBanana]

Dad always used the AC, always worked.

 

[woopedazz]

A/C. Fog is water condensing on the windscreen because of the difference in temperatures inside to outside. The A/C both dehumidifies the air so there are less water droplets to settle and reduces the temperature disparity. Quickest way to defog your car. Heater + A/C also works pretty well, but heater alone is the slowest way to defog.

 

[Jackfrost]

AC in and set air flow coming from outside car is the fastest and best.

 

[Scotland]

The quickest way to de-fog a windscreen is with a rag.

Can't guarantee clarity, but it's quick.

 

[Poseidon]

Cold air for the reasons woopedazz stated. Heat takes significantly longer.

 

[The Passenger]

Science has never been my strong suit, but I always thought the fogging was caused because the temperature on either side of the glass was different, ie: Outside is cold, inside is warm. I think you just have to get the glass to a consistent temperature. Or I could be completely wrong...

It certainly does piss you off though.

this is my understanding too.

think about whenever your shagging in a small room on a cold night. the windows fog up like crazy and you get your titanic moment. same principle in the car. heat on the inside, cold on the outside, you can titanic your windscreen.

whenever i crank the heat, it just fogs up more.

when i crank the cold, it clears.

i've found the best way to clear it is to open the window although it can be a bit on cold side. i am very good with cold, so if i got a jumper on as long it's 5 deg + i'll be fine. if i don't have a jumper, i'd rather it be 10+.

 

[Cruyff14]

OH MY GOD CAESER IS WRONG. STOP THE PRESSES.

 

[MrCharisma]

Air con, of course.

 

[RolandF1]

Air con, but I bought a new car recently and there is now just a front windscreen button which blows air when pressed.

 

[Messenger]

Having a raging debate on this with my brother.

I have always assumed you crank the heat, because the heat causes the fog to evaporate off the windscreen. He says crank the cold, because cold air is drier and works as a dehumidifier.

Who's right?

Can't believe this thread is still open. Shaking with rage.

 

[Simon_Nesbit]

I'm with Caesar on this one. Either will work eventually, but if the car is already warm when the fog comes in, then heat works far better. Heat will also help melt ice/sleet/snow if you are driving through it.

As stated before it's caused by the difference in temperature - so the options are either lower the temperature inside to match that outside (in which case, turn the AC off and just open the window!), or apply enough heat (and airflow) that the fog cannot condense.

Best option is heat and air-pressure. Second best is outside air - but that brings it's own issues.

 

[MisterB]

Climate Control knows best. Hit the Windscreen De-fog button and it fires up the AirCon along with heat assuming that the preset temperature is higher than current interior temp.

 

[lewigie]

Heat AND the aircon.

It's science, baby!

 

[Northworth]

Nelson Mandela had a view on this "a good AC and a good heater is a formidable combination"

 

[Jimmy1992]

I have always cranked the heat w/ AC and opened the windows. But, with the AC on it will always work.
I guess personal preference will depend what you do. If you can handle the cold, the AC by itself should, technically, work the fastest.

 

[The Passenger]

surely this is something they've done on mythbusters?

 

[Speck]

There's usually some sort of setting that will blow heat on to you, and cold air onto the windscreen. My car has this little snowflake button thing and if I press that it dehumidifies it.

 

[zimma]

I just use anti-fog on it... Tends to work fairly well.

 

[DrKrieger]

Air con FTW. My understanding is it's the dehumidifying component more than the temperature, if you really want to anger Bob Brown (or it's just really cold) then heater + A/C on works just as well as cold A/C in my experience.

 

[kfc1]

Pour boiling water on the outside of the windscreen

 

[brucetiki]

Heat with A/C - not only for the dehumidifying effects already mentioned, but it also gives the aircon a run in winter, preventing pump/seal issues caused by not using the aircon at all in winter.

 

[Stratton_Gun]

Theres a button is cars that just does it automatically.