vlad_a

I will have to agree that Toyota/Lexus has figured out the mildew problem. I never experienced it in my [long term] '03 IS300. Although I too have turned it off occasionally a few minutes prior to arriving to my destination, I haven't done it often enough to make an impact.

Looks like my constant battle with the auto-recirculation mode has another benefit:

rxsuperman

The design intent of RX HVAC system is to accommodate comfort all year round with minimal management of HVAC controls. In other words, on AUTO with compressor turned on, the driver or the passenger can simply adjust the temperature to achieve the desired comfort without excessive humidity no matter the season. There is no harm in running the compressor all year round (unless if you turned the fan off) because it's beneficial to circulate the refrigerant oil in the system to keep all the seals in good working order. The gas mileage difference between running the compressor, or not, is minimal or none.

MjThind

You don't have to go through the menu every time. When you press the auto button it turns on the AC regardless on the temp. See...
AC off...
http://i40.tinypic.com/2v0kf7t.jpg

AC on...
http://i39.tinypic.com/971tmu.jpg

Cruiter

What you're showing is how to turn the 'auto' on or off for detecting foreign matter in the incoming air and automatically changing from fresh to recirculation. Mine changes back and forth with the same light depending on how clean the air is. It has nothing to do with the compressor going on or off.

MjThind

That is what happens for me bud, CA air sucks it just stay on forever...

ecr72

It's not an AC button bud, it's for recirculation.

MjThind

I understand that but every time I press the Auto button by the recirculation button the AC turns on and when press it again it will turn off the AC...

kitlz

MjThind, the button is called the air intake control button. From the manual:

The manual also says the AC can be turned off by pressing and holding the down arrow on the fan speed. But that also turns off the fans. Once the fan speed is increased or the auto button is pressed, the AC will come back on.

vlad_a

I checked mine today and recirc turns on and off, opposite of the AC setting. Of course, it is relative to other factors, such as the outside temp. Recirc turns on to increase AC effectiveness.

Dolphin

I will throw my backing behind the "where is the AC Compressor button??" huh? One of many things on my 13 350 I simply don't understand. As others have mentioned, seems we go back in time instead forward. No Volt meter, no oil pressure gage? in 2013? They were all there in 1970.

This is the first car I owned without an AC switch. If it's cool outside, and warm in the cabin, which is very common on sunny days in spring / fall months. I like OA into the cabin, without the windows open, cause of the noise at high speeds. If you live in a dry climate, the AC further dehumidifies the "already dry air".... it's VERY annoying to have cabin full of 5% RH air. The RX gives you no option to overcome this annoyance. The design engineers need a lesson in HVAC or learn to read a psychometric chart, and learn to apply it to different parts of the world where these cars are sold.

As correctly pointed out, moisture on the evap. coil is the perfect breeding ground for all types of airborne microbes. Another reason to keep AC off when not needed. I HATE the smell that results from fungus / microbes growing on Evap. coil, and if you have allergies, it can be a real nightmare at times. Again, not everyone has allergies, so they will scoff at such a remark, cause, well, if it does not effect them, then it should not effect the rest of the population.

A simple fix for the microbe activity on the evap. coils, turn on heat HIGH, and try to burn off the microbes. Usually effective if left on long enough. It was an excellent suggestion by previous poster to turn off AC compressor before trip ends, to allow the Evap. coil to dry...always easier to prevent a problem, vs. combating it.

Agree with previous poster, NAV gave Lexus engineers a tool to overcomplicate the most simple tasks. I marvel how many things end users pick up on within a few days of owning the car, and yet, the design engineers work with these cars every day, ya wonder how much common sense they have....or why they work in a vacuum and don't solicit feedback from users, or just scroll through some forums. ?? (not just AC issue)

BobBass

Dolphin,

TERRIFIC post. I agree wholeheartedly.

Silvex

I think this is an important point made by ecr72

"Just because a light is on doesn't mean the compressor is running. "

I'm going out on a limb here, ready to be shot down!

I think ecr72 may be right.

I read somewhere that that green light only means that the compressor is either working, or on 'stand-by', right?

Similarly, Auto CC
The green light on that button does not always mean you have FULL Auto CC

You might have pressed the blower/fan touch screen buttons Lo - Med - Hi
The Auto CC light will still stay on.
But the system now is not, fully Auto.
Because you've just hard set the blower level.

Does vlad? accept this idea put forward by ecr72?

I'm a proud IS 250 F-Sport MY11 owner.
I have found this thread invaluable.

I've been wrestling for a long time trying to figure out what my HVAC is doing.
I'm getting there.

Sorry I'm late joining this very interesting party!

Silvex

websailor

We also like a much more manual control of the hvac in our car. We tolerate a fairly large range of temperatures and do try to use outside air as much as possible. So our vote would be for a simple AC on/off switch also.

I understand why the manufacturer would opt for a "run it on auto constantly" approach though - it is easier for most of their consumers (plus they are not paying for the cost of running it that way).

Ernie

DunWkg

You may not ever reach that point where you know exactly what yours is doing at any given moment. However, you can understand how it operates by reviewing the technical service manual or perhaps speaking with the technology person at your dealership.

Due to the copyrighted natural of the materials, I don't post whole paragraphs or sections from the manual here on the forum. Here is a sentence(s) from the HVAC description: "The neural network control consists of neurons in the input layer, intermediate layer and the output layer. The input layer neurons process the input data of the outside temperature, the amount of sunlight and the room temperature based on the outputs of the switches and sensors, and output them to the intermediate layer neurons."

My interpretation: When in full auto on a car with navigation, the system watches the temperature you have set, the actual temperature in the cabin, the actual outdoor air temperature, the sunlight sensor, the smog sensor, the fresh air switch and the A/C switch, plus whatever else and from that determines a mix of indoor and outdoor air, face and bypass damper position, blower motor speed, outlet damper positions and whether the compressor runs and at what speed it runs.

Again in my opinion, the A/C switch is an enable switch. It enables the compressor to run automatically. It doesn't mean it is running, just that it can run if so determined it is needed. The compressor is a variable speed compressor.

Personally I don't turn off the A/C switch and rarely do I use the fresh air / recirculation switch. I may use the F/R switch when following a foul smelling semi or on a gravel road, although I'm not sure the outdoor air intake ever closes completely. There's probably some industry standard or legally required minimum of fresh air.

The above discussion is relative to the 2010-2012 model year. Things may change by model year.

Silvex

David, thanks for this.
It has immediately furthered my understanding.
I note your caveat at the very end, "The above discussion is relative ... "

<You may not ever reach that point where you know exactly what yours is doing at any given moment. >
Yes, I realise and accept that.
But it does not deter me from finding out as much as I can.
I have studied and continue to study, any technical material I can get my hands on.

<... ......or perhaps speaking with the technology person at your dealership.>
Hmmm, ........ Yes, I should do that I suppose :-)

<Due to the copyrighted natural of the materials, I don't post whole paragraphs or sections from ...>
Yes, understood.
That has to be correct.

<""The neural network control consists of neurons in the input layer, ..... "
Wow!
I'd heard about this.
I don't understand it.
Just like I don't understand the Artificial Intelligence Shift technology in our gearboxes!
There seems to be an awful lot of sensors and processing of their inputs in our cars.
I just think it shows the wonderful complexity of the technology we are trying to understand.
Quite daunting, for a non-technical person like myself.

Thanks very much for your interpretation.
That's very helpful to folks like me.

<It enables the compressor to run automatically. It doesn't mean it is running, just that it can run if so determined it is needed.>
I'm so glad you've confirmed this.
It has been troubling me for a while.
Although I note that you say, "..in my opinion, ..."

Dare I ask you to tell us what your technical service manuals say?
I'd really like to nail this.

<Personally I don't turn off the A/C switch ...>
Ok, noted.
I'm experimenting at the moment with A/C off.
Just outside air. Dash vents directed to face. Everything else Auto.
It's 6C here at the moment. Cold.
I'm pleasantly surprised as to how comfortable it is!

Peter