# Automotive Air Conditining **URL:** \ **Category:** Factual Questions\ **Created:** [July 26, 2019, 7:11pm UTC](https://boards.straightdope.com/t/automotive-air-conditining/837682 "2019-07-26T19:11:51Z")\ **Posts on this page:** 7\ **Page:** 3
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [July 28, 2019, 12:37pm UTC](https://boards.straightdope.com/t/automotive-air-conditining/837682/41 "2019-07-28T12:37:21Z")
> [@Gary\_T](#): > > … > > In recirc with the A/C off, the moisture from people’s breath builds up inside the cab so of course it fogs the windows. Don’t do that. You really need to learn how AC works. It doesn’t just cool the air, it removes moisture. That’s why it’s called air _conditioning_. Hence moisture from people’s breath _will_ get removed. Your “analysis” of the problems with recirc is flawed. Running air from the AC over your windows removes window fogging, after all. (But it chills the windows so if you turn it off the fog returns quite quickly.) ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [July 28, 2019, 1:02pm UTC](https://boards.straightdope.com/t/automotive-air-conditining/837682/42 "2019-07-28T13:02:03Z")
> [@ftg](#): > > You really need to learn how AC works. You really need learn how to read what you’re quoting. > [@](#): > > It doesn’t just cool the air, it removes moisture. That’s why it’s called air _conditioning_. Hence moisture from people’s breath _will_ get removed. > [@Gary T](#): > > In recirc with the A/C off, the moisture from people’s breath builds up inside the cab so of course it fogs the windows. Don’t do that. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [July 28, 2019, 8:09pm UTC](https://boards.straightdope.com/t/automotive-air-conditining/837682/43 "2019-07-28T20:09:40Z")
> [@Joey\_P](#): > > You really need learn how to read what you’re quoting. Easy for you to say … 😉 ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [July 28, 2019, 11:17pm UTC](https://boards.straightdope.com/t/automotive-air-conditining/837682/44 "2019-07-28T23:17:41Z")
> [@ftg](#): > > Easy for you to say … 😉 Also, rereading what I said, I didn’t mean to come off that harsh, I was just using the same words.:o ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [July 29, 2019, 3:07am UTC](https://boards.straightdope.com/t/automotive-air-conditining/837682/45 "2019-07-29T03:07:13Z")
> [@ftg](#): > > You really need to learn how AC works. I’ve been working on automotive A/C professionally for over 45 years. Apology accepted. 🙂 ---
**Author:** ![sps49sd](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@sps49sd](https://boards.straightdope.com/u/sps49sd)\ **Post date:** [July 29, 2019, 5:47am UTC](https://boards.straightdope.com/t/automotive-air-conditining/837682/46 "2019-07-29T05:47:40Z")
> [@Enola\_Straight](#): > > I once had a mid to late 80s Acura Integra with separate push-button controls for re-circ and AC. > > One bitter-cold night I put on recirc but no AC and my windows fogged up; punching in AC and fresh cleared up the windows in minutes. AC removes moisture, hopefully everyone realizes that by now. What you and others upthread experienced is vapor condensing on the glass surfaces which are colder than the air. The air reaches its dewpoint at those cold surfaces but generally not where air is moving over the glass by the air duct outlets… ---
**Author:** ![Snnipe\_70E](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@Snnipe\_70E](https://boards.straightdope.com/u/Snnipe_70E)\ **Post date:** [July 31, 2019, 5:33am UTC](https://boards.straightdope.com/t/automotive-air-conditining/837682/47 "2019-07-31T05:33:55Z")
> [@Grrr](#): > > The problem with that is it creates a negative air pressure Wich draws in warm air from outside. It also loses efficiency by cooling air that’s already cool. How does it create a negative pressure. [Previous page](https://boards.straightdope.com/t/automotive-air-conditining/837682.md?page=2)