Silvex

For some time now, I've been storing up a lot of questions on the automatic a/c controls on my IS250 F-Sport MY2011 (Euro spec)

Section 7 of the Navigation System Owner's Manual is nearly as bad in explaining things as the "Radio operation" sub-section of Section 6, "Audio/Video System".

To start with.
Page 272, "Switching between outside air and re-circulated air modes"

That says when the system is switched to automatic mode (by pressing the air intake control button to give automatic mode), _the a/c system operates automatically_.

Why does that happen?
What is the purpose of it?

Silvex

UniSlayEX

The vehicle will automatically choose between recirculation of air in cabin (the arrow inside the car) or draw air from outside the vehicle (arrow going from outside car to inside). Why? multiple reasons, for instance:

its 85* outside and you want it cooler, say 72* (sorry i know youre metric but i dont want to do math)

when in auto, the cabin will recirculate the already cool air until the desired temperature is reached then begin to pull air from the outside.

If you travel to an area with a peculiar smell or have seasonal allergies, you may not want that vent to open up so auto can be turned off to allow the occupants to deem whether they want the vents open or not.

Silvex

Thanks.
I understand all that you have said.

But I would still like to know :

why, when the system is switched to automatic mode (by pressing the air intake control button to give automatic mode), _the a/c system operates automatically_.

In other words, why does the a/c have to be on for the automatic air intake mode to work?

Btw don't worry about metric Centigrade.
Seeing reference to Fahrenheit is quite nostalgic for me.
Good times :-)

Silvex

UniSlayEX

That I can not tell you because I have no idea other than that is how it controls the temperature. Even when you have it set warmer the A/C stays on even though it is not in use. Hopefully someone more experienced with the system can chime in.

Grambo

Well...if it's 100 degrees outside and you want it to be 65 degrees in your cabin...that's not going to happen without the use of the A/C. The car is automatically going to calculate what it needs to do to get to your desired temperature as quickly as possible.

Silvex

Ok
It's a tricky one isn't it?

"Even when you have it set warmer the A/C stays on even though it is not in use."
Yes, I've noticed that too.

"Hopefully someone more experienced with the system can chime in."
Yes, again. Or someone with a good technical knowledge of aircon systems in general must
know the answer.

We will get to the bottom of it I'm sure.
There are some really good people using this forum.

Silvex

Silvex

Thanks. Yes, I understand and agree that.

".... that's not going to happen without the use of the A/C."
But what has automatically activating/switching on the aircon got to do with automatic air intake circulation?

Silvex

Silvex

Grambo, just another thought that might help explain my query.

You can activate "Auto" (that's the physical button at the left hand side (UK)! of the bank of air and heating buttons in the dash) even when you are in non-a/c mode, right?

Have the Lexus engineers set it up so that it defaults to a/c on?
That is, when you press the middle button "Auto" in the bank of three air intake buttons,
Most of the time that is what you would want.
Fine.

What I mean is this.

Say you are in non-a/c mode.
When you press the middle button "Auto" in the bank of three air intake buttons, a/c would come on.
That is the default.
To turn a/c off you need to press the on screen "A/C" button, bottom left.

Does that make sense?

Silvex