Wouldn't the system have more wear on it when trying to constantly cool the air coming in from outside with recirc off? Seems to me you are getting a steady influx of warm air from outside the cabin, and it never gets to your desired temp b/c basically it has to cool the entire world (or at least the part in oyour path constantly moving into the cabin.

I don't think I've even owed a car in my decades of driving where I turned the AC on, and left the recirc off.

In my mind recirc closes the air in the cabin, then "treats" it...either cools it or heats it, etc.

 

You are correct that if warm air influx is chocked, the closed air gets cooler at a faster rate.
Caveats are:
Even in recirc fresh air is still introduced at a reduced rate.
The cooling is strong enough to compensate for the hot air outside that is being pulled in.

Engineers have determined the amount of fresh air that needs to be pulled in for health of occupants. Trust me those Lexus guys have done a fine job [my middle east example stated before].

Many years ago, I would lower the windows to air out the hot air in the parked car in Sun.

Salim

 

I too have this problem. However, it’s a new problem. I’ve had this car for over seven years and it has stayed on recirculated air. I have the bottom auto button set. And the button on top of that recirculated air/auto/fresh air I always have set to recirculated air. In the past few months, I have replaced catalytic converter, O2 sensors, and a gasket to fix a small leak in the exhaust. However, my car automatically shuts off recirculated air and puts the car into the auto fresh air mode. It’s super frustrating because it never did this before. Any advice?

 

Take my input as just one piece of information. Other can share their experience to help you formulate an opinion.

My understanding is that with AUTO the recirc is under the control of the HVAC system. That system will prefer to get the fresh air in. You may be able to set the override but when ever the software takes control it will default to making the choice with the preference of fresh air. [It could be 12v was removed for the stated work and boom the software took the control]. Basis of the above is when I leave the settings on AUTO the computer in case of extreme heat will go on in recirc on its own and blower at full speed, vents blowing through the high vents and after a bit of cooling the the blower will slow down, the recirc will select outside air and the vents will go hunting the best air redirection.

Personally (used here for myself only) I have conceded that the HVAC settings in Lexus are so intricate and perfected that anything I do to override, I will hit the Auto button soon.

We can have a discussion on your choice of selecting Recirc setting, but how the HVAC system behaves is hidden in the software control of the system.

Salim
I am not sure if 3rd gen RX has the auto recirc selection based on outside pollutant sensor [my ex 98 GS had that]. That may be influencing previously and kept the vehicle in Recirc mode for you.

 

I have had a couple of prior vehicles that would make similar fresh air vs. recirculated air HVAC decisions on their own regardless of what manual input I attempted to initiate. I finally decided just to let them do their own thing and quit trying to fight it.