does it bug anyone else that the climate control always switches from fresh air to recycled after the car is turned off.

or is this just on the ealier models? I just want eveything to stay the way that they where when I turned the car off .. its trying to be smart I guess .. changing it to recycled ..
I suppose this is normal ?

assuming the temp is set to coldest?

 

I think this can be programmed at your Lexus dealer. Call them up. Do a search on the settings available for your car while you're at it.

 

Mine does the same thing. I have a '92. Even when i switch it over to "fresh" air a few seconds after i start the car, it will automaticly switch back a few seconds later.

 

Stupid Japanese thery strikes again.

Their idea is this, it's hot outside so why pull in more fresh (HOT) air that has to be cooled at the same time all the interior materials and surfaces must be cooled in order to reach a reasonable human comfort level.

It apparently has never occurred to anyone to leave it on fresh long enough to purge the hot(ter) air already in the car and then convert to recirculate mode once the interiro atmosphere is at or below the outside air temperature.

But, having said all of that, your Lexus climate control will automatically reset to fresh mode (if that's where you had it to begin with) once the A/C has succeeded in cooling the interior down to your comfort level.

 

mine does that sometimes.....but most of the time it stays where I leave it....gotten better lately.....wierd..

i'd like to know what the deal is....If anybody gets this fixed please post...

 

Mine remembers the position I left it in, if the key is cycled. However the auto function does toggle the setting if I had it on fresh when I drive to work in the morning, and then come back in the afternoon and its hotter than hell.

As for stupid Japanese theory, you're neglecting latent heat removal. In the fresh mode, a decent portion of the system capacity is dedicated to dehumidifying the incoming air. In recirc, once the cabin has been dehumidified, most of the system capacity is available for sensible heat removal.

The optimal solution would be to engineer a rain sensor, and window and sunroof control into the system, allowing the climate control to roll down the windows and tilt up the sunroof to purge the hot air from the car, when its not raining of course.

 

On a bright sunny day the temperature inside the vehicle might rise to 100F+ while outside temperatures remain in the 70s. Stupid to "lock" that HOT air inside with reciculate while cooling it down to 70F when outside air is already at 70F and can be chilled below that as it enters. It would be better to leave the system in fresh long enough to purge the "super-heated" interior atmosphere and then swicth to recirculated airflow to continue cooling the interior.

 

I drove around with a thermometer stuck in the dash vent of my car for a few days. Every time I put it on fresh, the temperature drop of the system went down to about 35 degrees. In recirculate mode, it was 50 degrees or better. Consider temperature drop in conjunction with the increased airflow of the recirculate mode, and you're getting far more heat removal in the recirculate mode. Moreover, the volume of air flowing in from outside is not sufficient enough to exchange the entire contents of the cabin faster than the system can remove the heat in recirculate mode. The opening at the base of the windshield is not even 1/2 a square foot, plus the blower doesn't source all of its air from that from outside when in fresh mode, part of the cabin air is being recirculated. *THEN* consider that the cabin is pretty much airtight as far as exhausting the hot air is concerned, and you cut down on the fresh air exchange even more. Try popping the sunroof into vent mode on the highway, with the climate control in fresh mode, and see how much more air comes through the system.

Neglecting humidity, the system would perform better as you suggest. Of course that limits your "improvement" to the realm of theory since very few places have no humidity, and a need for A/C at the same time.

 

I think you might be hearing a lot more air movement "noise" in recirculate mode and confusing that for air movement "volume". More noise often, as is mostly true in this case, indicates turbulent airflow not necessarily a higher volume of airflow.

But your point is well taken, in order to improve MPG numbers Lexus, like Boeing, has minimized the level of outflow to the absolute minimum. So lowering the rear windows slightly, and/or manually increasing the blower speed in "fresh" will substantially increase the rapidity with which the hot air in the car is purged.

In the 91, 92, and 95 LS, the 00 & 01 RX, and the 00 GS3, the recirculate door is COMPLETELY CLOSED unless the climate control is in the discussed (automatically flipped to recirculate for supposedly quicker cooldown) mode. The ONLY source for airflow through the blower is from outside. Actually, at least in the above named cars, in (automatic) fresh mode the recirculte door only begins to open as the interior temperature approaches the setpoint temperature, at first only slightly and never more than about 30%

You seem to be saying that cooling a trapped volume of air from 130F to 70F, while simultaneously cooling the interior materials and surfaces to a human comfort radient and contact level is more efficient than starting out with 35F airflow to begin with.

I don't think your theory holds water.

 

Yes, there is more noise, but there's defintely a greater volume of air coming out of the vents as well.

The SC shop manual states that there are 3 positions for the air mix door...full recirculate, 1/2 recirculate, and no recirculate.....it doesn't state the criterion for determining the 1/2 position. I think the SCs have a rather abrupt switchover to fresh, not the gentle glide you describe in the other cars...I can defintely tell when the system switches over to fresh or 1/2 fresh, because I can feel and smell the moisture.

I'm going to let my car get nice and toasty in the parking lot tomorrow at work and see what my thermometer says about system performance in fresh v recirculate.

 

If you have an A/C incoming air filter then you can remove it and watch the various degrees of the recirculate flap opening as you manipulate the temperature setpoint.

A simple thermometer isn't going to tell you all that you need to know. The human body's comfort level is affected just as much (sometimes moreso) by radient heating/cooling from its surrounding environment as it is by local temperature (and humidity).

Think of yourself in a clear plastic bodysize chamber (remember Superman II?) with the chamber air temperature at your (normal) personal comfort level (72F{?})but within an icehouse surrounded by frozen blocks of ice.

You would be shivering with minutes if not seconds.

That's because your body is continuously radiating heat outwards but in this case getting nothing in return.

For your test you will need to determine the MRT (Mean Radient Temperature) and the atmospheric air temperature at your seated position.

You will not be fully comfortable until the "surround", material and objects within the vehicle, is cooled enough that it is no longer radiating heat to your body and your local atmosphere is at your comfort level.