Air Intake Control And Air Conditioning

Argento · July 8, 2013

Help please.

I'm having trouble understanding what the connection is between my air intake control button and the air con system.

As you know, 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?

I posted this in the IS250 etc. section about three weeks ago.

I got absolutely nowhere.

I believe only the IS 250 F-Sport (my car MY2011) has this air intake control button automatic mode feature.

That's probably why most people there (IS do not know what I'm talking about!

I do know that the IS-F has the feature.

Argento

ColinBarber · July 8, 2013

if this is like the systems in the GS and LS etc. then the system will automatically sense polluted air and automatically switch to recirculation mode until it is clean again. It is useful when you are stuck behind diesels :)

On the GS if you press and hold the button for a few seconds you can adjust the sensitivity.

The system needs the aircon system to operate and so will turn it on when selecting auto if it isn't on already.

stevet · July 9, 2013

Plus when its really hot it will automatically go into recirculate so you are cooling cooled air to get the cabin cold asap.

MrW · July 9, 2013

Plus when its really hot it will automatically go into recirculate so you are cooling cooled air to get the cabin cold asap.

Just this, speeds up cooling down and heating up when you have the climate in auto mode. Once cabin temp has reached correct temp it returns to normal. I think it engages recirculate when you press that extra filter button too.

Argento · July 10, 2013

if this is like the systems in the GS and LS etc. then the system will automatically sense polluted air and automatically switch to recirculation mode until it is clean again. It is useful when you are stuck behind diesels :)

On the GS if you press and hold the button for a few seconds you can adjust the sensitivity.

system needs the aircon system to operate and so will turn it on when selecting auto if it isn't on already.

"if this is like the systems in the GS and LS etc. then the system will automatically sense polluted air and automatically switch to recirculation mode until it is clean again. It is useful when you are stuck behind diesels :) "

Yes, that's exactly what happens on my car.

It works extremely well doesn't it.

I like your bit about the diesels, as you would expect!

"On the GS if you press and hold the button for a few seconds you can adjust the sensitivity."

Yup. Same.

No problem with that. Very easy to use. A great feature.

".... system needs the aircon system to operate and so will turn it on when selecting auto if it isn't on already."

Now, this is what I'm trying to get at. ... ....

My question is - why does the (air intake control) system in automatic mode, need the aircon system to be on?

Silvex

normski2 · July 10, 2013

Exhaust Sensitivity setting the same on my is250 SEL (2010)

ColinBarber · July 10, 2013

My question is - why does the (air intake control) system in automatic mode, need the aircon system to be on?

Silvex

In theory it doesn't need to be on, it is just how it is designed. Possibly to avoid any fogging situations or to avoid turning on the aircon system for a very short time period when switching into recirculate mode and then out of again which can happen within a few seconds.

Argento · July 11, 2013

This response from ColinBarber really gets to the nub of my query.

"In theory it doesn't need to be on, it is just how it is designed."

Ok, I get that. Thanks.

"Possibly to avoid any fogging situations or to avoid turning on the aircon system for a very short time period when switching into recirculate mode and then out of again which can happen within a few seconds."

Yes, I can see that both are very plausible explanations.

Lexus/Toyota do seem to go on a lot about "fogging" in their Owner's Manuals don't they?

More of a problem in other countries than ours perhaps?

Presumably we will just have to be satisfied with our speculation

and "Possibly... .." ?

We are not going to get a definitive answer from Lexus/Toyota are we?

BTW Colin, how did you come to the conclusion of your "Possibly"?

Argento

Argento · July 11, 2013

Exhaust Sensitivity setting the same on my is250 SEL (2010)

Yes, my mistake.

I said I thought that only the IS-F and IS250 F-Sport had the auto air intake feature.

I was mistaken.

Argento

ColinBarber · July 11, 2013

I've been unable to find an official explanation in any workshop manual or new vehicle guide why AC is required, only that it is required for the feature to operate.

What I do know is it isn't a technical reason around the feature itself. The exhaust gas sensor, or smog sensor, that is used to measure the air quality sits at the front of the vehicle exposed to the outside air. It isn't that the sensor needs to received dehumidified air to work which means it has to sit within the cabin airstream with the AC running. Therefore the ability to detect and react to the air quality is in no way directly related to the aircon.

When you switch off the aircon system, any moisture which has collected on the evaporator has the chance to be drawn into the cabin and so you can get some fogging. This is why I thought this could be a plausible reason.

It could just be that the auto-recirculate feature is seen, from an engineering or marketing standpoint, as an extension of the auto climate control system and as such a person wanting to pay for, and use, such a system is the type of person who just wants the luxury of enabling the system and forgetting about it - not manually enabling and disabling AC in a reactive way when they get too hot or cold.

Argento · July 12, 2013

I've been unable to find an official explanation in any workshop manual or new vehicle guide why AC is required, only that it is required for the feature to operate.

What I do know is it isn't a technical reason around the feature itself. The exhaust gas sensor, or smog sensor, that is used to measure the air quality sits at the front of the vehicle exposed to the outside air. It isn't that the sensor needs to received dehumidified air to work which means it has to sit within the cabin airstream with the AC running. Therefore the ability to detect and react to the air quality is in no way directly related to the aircon.

When you switch off the aircon system, any moisture which has collected on the evaporator has the chance to be drawn into the cabin and so you can get some fogging. This is why I thought this could be a plausible reason.

It could just be that the auto-recirculate feature is seen, from an engineering or marketing standpoint, as an extension of the auto climate control system and as such a person wanting to pay for, and use, such a system is the type of person who just wants the luxury of enabling the system and forgetting about it - not manually enabling and disabling AC in a reactive way when they get too hot or cold.

<I've been unable to find an official explanation in any workshop manual or new vehicle guide why AC is required, only that it is required for the feature to operate.>

Ok.

I'll stop looking for an official answer then.

That will save me a lot of time. Thanks.

We will have to live with " ... it is required for the feature to operate." That's fine.

This suddenly dawned on me last night when I was out in the car.

The Re-circ feature is there not only to control exhaust fumes.

It also plays a key part in the A/C system, right?

Last night, A/C and Air Intake Control were both on Auto

Outside Air Temperature after a hot day of 24C here, was 16C

The Air Intake Control indicator light bounced around two or three times during my short journey home, 6 miles.

That is to say, bouncing from "Auto and, through-car" to "Re-circ"

I was driving along traffic free roads in deep and beautiful English countryside on a Summer evening!

So, no exhaust fumes or 'farmy' or other outside odours, as far as I could tell.

Conclusion.

The indicator light was moving around purely because of the demands and call of the A/C system.

The Auto A/C system will decide which air supply (through-car or recirc) will best achieve the selected cabin temperature at a particular point in time.

Sometimes it will choose to re-circulate and continue to cool (or heat) the air in the cabin.

At other times, it will choose to cool the ambient air coming into the car.

Have I got this right?

I buy all of this.

Particularly, ".... the type of person who just wants the luxury of enabling the system and forgetting about it - not manually enabling and disabling AC in a reactive way when they get too hot or cold."

It really does seem that the Auto Re-circulate feature on our cars could well be an extension of the auto climate control system, doesnt it?

Also, the engineers and or marketing folks might have thought the benefits of having a/c off (fuel saving), does not outweigh the benefits of driver ease of operation?

We're speculating again :-)

But what else can we do?

Nobody else knows do they ... .......

Argento

Argento · July 12, 2013

Moderators, your help would be appreciated please.

My last post seems to include some odd "white" highlighting of text?

My fault, because I was having trouble with my fonts when composing the post!

Could you fix it for me please?

Thanks, Argento

Argento · July 12, 2013

Plus when its really hot it will automatically go into recirculate so you are cooling cooled air to get the cabin cold asap.

Yes.

That makes good sense doesn't it.

Argento

Argento · July 12, 2013

Plus when its really hot it will automatically go into recirculate so you are cooling cooled air to get the cabin cold asap.

Just this, speeds up cooling down and heating up when you have the climate in auto mode. Once cabin temp has reached correct temp it returns to normal. I think it engages recirculate when you press that extra filter button too.

Argento · July 12, 2013

Plus when its really hot it will automatically go into recirculate so you are cooling cooled air to get the cabin cold asap.

Just this, speeds up cooling down and heating up when you have the climate in auto mode. Once cabin temp has reached correct temp it returns to normal. I think it engages recirculate when you press that extra filter button too.

Yes. thanks.

That's really important to know and understand I think.

I notice that you say "heating up".

That's right of course.

Some tend to think of "air con" as just cooling don't they?

But in the world of Lexus/Toyot at least, it is both cooling and heating isn't it.

Argento

Argento · July 12, 2013

Plus when its really hot it will automatically go into recirculate so you are cooling cooled air to get the cabin cold asap.

Just this, speeds up cooling down and heating up when you have the climate in auto mode. Once cabin temp has reached correct temp it returns to normal. I think it engages recirculate when you press that extra filter button too.

I also meant to say.

" I think it engages recirculate when you press that extra filter button too."

If you meant the pollen filter, then I believe you are correct.

Argento

Argento · July 12, 2013

My question is - why does the (air intake control) system in automatic mode, need the aircon system to be on?

Silvex

In theory it doesn't need to be on, it is just how it is designed. Possibly to avoid any fogging situations or to avoid turning on the aircon system for a very short time period when switching into recirculate mode and then out of again which can happen within a few seconds.

"... or to avoid turning on the aircon system for a very short time period when switching into recirculate mode and then out of again which can happen within a few seconds."

Are you saying that the air con might be on all the time?

Or at least, ready and available to be called when needed?

Blimey, I'm starting to talk like the heating engineer who came to service our gas boiler yesterday :-)

Argento

Argento · July 12, 2013

Plus when its really hot it will automatically go into recirculate so you are cooling cooled air to get the cabin cold asap.

Just this, speeds up cooling down and heating up when you have the climate in auto mode. Once cabin temp has reached correct temp it returns to normal. I think it engages recirculate when you press that extra filter button too.

Yes. thanks.

That's really important to know and understand I think.

I notice that you say "heating up".

That's right of course.

Some tend to think of "air con" as just cooling don't they?

But in the world of Lexus/Toyot at least, it is both cooling and heating isn't it.

Argento

normski2 · July 13, 2013

Indeed, on a cold morning you may find warm air coming into the cabin if say, the temp was set to 21degrees.

stevet · July 13, 2013

Indeed, on a cold morning you may find warm air coming into the cabin if say, the temp was set to 21degrees.

Most importantly 'dry' warm air.

Argento · July 14, 2013

A quick question, while I'm still getting my head around this.

For cars without Automatic Air Intake Control e.g. IS220d

Do they still get recirc and outside air automatically, when they are in Automatic Air Conditioning mode?

Argento

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Argento · July 14, 2013

Indeed, on a cold morning you may find warm air coming into the cabin if say, the temp was set to 21degrees.

No sorry, I don't get this?

Are you pulling my leg :-)

I _would_ expect warm air coming in (if the engine was warm) on a cold morning wouldn't I ..... ?

Argento

normski2 · July 14, 2013

Indeed, on a cold morning you may find warm air coming into the cabin if say, the temp was set to 21degrees.
Most importantly 'dry' warm air.

Quite so

normski2 · July 14, 2013

If its cold outside overnight, then the cab will be cold in the morning. So if you drive to work with the temp sat at what you think is a nice cool temp, say, 20 degrees then the air con will pump warm air(dry) into the cab to elevate the temp to 20 degrees. Can be a bit of a shock if you are unaware how sensitive the setting can be.

First time I noticed it I thought I had a faulty system...then I realised I was being a plonker and not paying attention to the settings I had set.