satnav

Can someone explain to me why automatic climate control always blows what it seems heat from the floor when its cold and a/c from the upper vents when its warm? I never understood whether on my Audi or the current car I have now Lexus they all seem to do this. Why can't automatic climate just blow from all vents? Or allow me to choose while keeping the auto light on.

Also on my Lexus I had the dealer turn off get air from outside through personalized settings. I only like it running recirculate mode, but I noticed when its really cold the car seems to override and pull outside air in. Why does it do this? And is it bad I just turn recirculate back on every time the car turns it off. BTW don't have auto recirculate option.

Personally to auto recirculate does not work I had it on my Audi and it would sense smog to late, so I just run the car in recirculate mode anyways.

tex2670

It's not the greatest idea to have fresh air mode permenantly disabled. Recirculated air has more carbon dioxide, and can potentially lead to drowsiness, especially on a long drive. You might be better off closing the center dash vents.

FrankReynoldsCPA

I've never really understood that myself either. I found AUTO to be useless on my 92 LS400. I didn't like that it always ran the compressor, whether i was using heat or a/c. It also would never blow as hard as if I just ran it on high.

My guess about the choice of vents might be something to do with the fact that warm air rises? Or maybe because it's nicer to just have an ambient warm setting than to have hot air blowing in your face.

tex2670

I find it works better changing the mode to floor and defrost combo, rather than floor/face.

FrankReynoldsCPA

Yeah, that was a decent combo.

My Fusion doesn't have auto climate control(about the only option on my trim level that I don't have, I think). I'm just ok with that, since I gave up using it on the LS.

satnav

Yeah the auto climate on Lexus cars are not as good as on the German cars.

FishBike

Warm air rises, so heating from upper vents only = cold feet. Conversely, cold air sinks, so if you have air conditioning from the floor vents you get cold feet again. Auto climate control does it the way it does to make the temperature more consistent from the ceiling down to the floor. I've always operated my manual climate controls that way as well.

I've only had a couple of cars with auto climate, but both have allowed manual override of the vent settings while leaving outlet temperature and fan speed on automatic. Though the "auto" light does go off as, I guess, that's more of a "full auto" light.

As for outside vs. recirc in very cold weather, if you have it on recirculate your windows will fog up inside. Or will be more prone to doing that. So I guess they are trying to protect you from that problem?

LexBob2

I used to always fiddle with the auto climate control. Lately I 've just been leaving it at 70-72 and let it do its thing. It's been working well for both my wife and me winter and summer.

tex2670

...not as good as Hondas either...

tex2670

Except that I find in my Lexus, after the initial heat up in Winter, cool air starts to blow out of the upper vents.

chikoo

Elementary Physics, mi lad.
Cold Air flows down, hot air rises up.

chikoo

The best one till date: 2003 Mazda6 v6. It had a feature where if you set it to 77, it will keep the car cabin at comfortable feeling like normal room temperature, no matter how hot or cold it was outside. Amazing.

Other cars I have had are 2000 ES300, 2001 RX300, 2008 IS250, 2010 ML350

Silvex

< Can someone explain to me why automatic climate control always blows what it seems heat from the floor when its cold and a/c from the upper vents when its warm? >

I must be missing the point here.

Why would you not want heat on your feet when it's cold?

Similarly, why would you not want cold air in your face when it's warm?

I don't get it.

Silver

Silvex

FishBike, < Though the "auto" light does go off as, I guess, that's more of a "full auto" light. >
Just wanted to let you know, that's real helpful to me.
Thanks.
It makes sense.
I'm trying to understand recirc and outside air modes, air intake control button functions etc. etc. in our cars.
I'm getting there, thanks to CL :-)

Silvex

natman

I'm going to guess that the Climate Control is trying to defrost the windshield by turning on the AC. This is a great trick when needed, but manufacturers have become obsessed with it, forgetting that if the windshield needs defrosting it's probably cold enough that the passengers (remember them?) don't want the AC on more than is absolutely necessary.