bostonsnow

I have been trying to figure out the details of how the climate system works, which is not easy even reading the full size manual.

The digital on screen controls make sense.
The hard push buttons on the dash are a bit unclear. There are two "auto" buttons. One is on the higher row along with the majority of the climate buttons. That seems to turn on true AUTO mode. Then there is another AUTO button in between the recirculate and external air intake control. Does that do something different, or does it turn on the same AUTO feature?

Also, on the menu option to change options, there is a "pollen and mico dust" filter that can be turned on. Very sparsely explained in the manual. The manual says that even without this turned on, pollen gets filtered. So then what happens exactly when you do toggle this option on and off??

thanks for insight if anyone has these things figured out.

jollick

The upper AUTO controls temperature and where the air comes out, floor, dash, or both. The lower AUTO monitors smog and will switch between inside and outside air depending on outside temperature and smog readings from a sensor. I cannot comment on the filtering as I am not sure.

bostonsnow

ah ha - that explains why the bottom AUTO has always gone to recirculate - I am in LA so the smog levels probably are rarely low enough to switch to external air!

Arty101

The upper Auto controls fan speed. The lower Auto controls the recirc/fresh and ac. You can change the sensitivity of the smog sensor to go the fresh air mode sooner, but it's also dependent on your temp setting and the outside temp.

lesz

The auto that is on the recirculate-fresh air button is set to default to recirculate whenever the outside temperature is above the low 70s, which is confirmed in the vehicle manual.

Many of us have found that this default behavior of continuously running in the recirculate mode can result in stale air quality in the cabin, and,unfortunately, there is no way to change that default behavior. Since the system defaults to recirculate every time the car is started and auto AC is being used, some of us have gotten into the habit of manually changing the fresh air/recirculate setting to fresh air every time we restart the car.

The main reason why Lexus designed the system to default to recirculate is that, by doing so, Lexus is able to gain a very small increase in its EPA fuel economy rating, but the price for doing so is that stale air can be continuously recirculated through the vehicle.

bostonsnow

thanks Lesz, this is actually exactly my concern and what I don't want. I usually do not like recirculate unless it is super hot out, or if I am driving by something very smelly or a car with very bad fumes.
I almost always prefer fresh air.
In my 05 Es, the way to prevent this same thing happening was not not use the Auto AC mode.

for my ES300h, I will change the vehicle default setting of "AUTO AC ON" to "AUTO AC OFF" to see if this prevents the re circulate from defaulting every time the car starts up. I know this will prevent the AC coming on automatically, but lets see if it keeps the car in fresh air mode rather than going back to re-circulate.

lesz

Unfortunately, if, in the climate control custom settings, you change it to "auto AC off", you will be doing the exact opposite of what you want to do because, with that setting, the climate control system will constantly use recirculate mode whenever the AC is on, and you can't even manually change it to the fresh air setting.

What is also true is that, while having the system default to recirculate (with AC on and outside temperatures above 75) allows Lexus to get a very small increase in mpg in the dynamometer testing used to determine EPA ratings, in the real world, the recirculate default setting can actually result in lower mpg than you would get with the fresh air mode. The reason is that, if the car has been sitting in the sun, the in-cabin air temperature can reach 130 degrees or higher, and, when you start up the car and the AC is trying to cool off the cabin, the compressor needs to run longer with that 130 degree air being recirculated than it would if it was bringing even 95 or 100 degree fresh air into the cabin.

bostonsnow

thanks!
agree fully on the latter point.
Recirculate, IMO, is only good when its an extremely hot day, and you already have your car interior air cool, so you want to re-use that cooled air!

When your car is parked in a hot place, it is dumb to recirculate air that is hotter than the outside! that's why I have always preferred manual control on recirculating.....
oh well......

zes

Also recirculating air continuously appears to cause mold to grow in the AC evaporator. See other threads.