[blackie]

Did a search but didn't come up with the answer:

The auto climate control is cool. I was wondering whether the 'auto' setting also activates the 'max cool' prgramme and the 'auto air recirc' when it senses it needs them?

The manual isn't conclusive on this.

Also: when in 'auto', does the climate control also switch off the 'cooling' action if it doesn't need it? If a car is cold enough it's such a waste of fuel and power to have air con on if just blowing or heating is required to get the right temperature.

I guess I'm asking if it's fully 'auto' or do you find yourself touching the 'max cool', 'AUC' and defrost buttons to get the settings and features you require.

[wheeler]

The system won't know when the air is smelly or dirty to automatically recirculate instead of bringing in outside air. There's a button on the steering wheel for you to activate if you see a cloud of diesel smoke belching out of the bus in front of you.

If you just hit the 'auto' button the AC will kick on and stay on. It will mix AC and hot air together to give you air the right temp, and it will simultaneously dehumidify your interior on a rainy day. But it will also lower your fuel economy.

If you hit 'auto' then turn off the AC component by pressing the 'snowflake' switch, it will use the heater to warm it up if below the desired temp, and blast the vent fans if it is above, without using AC.

If you hit "def,' it will blast both the heater and the AC through the window ducts at highest volume and temp to clear your windshield really fast. Once you can see, you'll want to shut it off and use your standard climate controls to regulate condensation buildup.

[TYW]

Originally Posted by wheeler

The system won't know when the air is smelly or dirty to automatically recirculate instead of bringing in outside air. There's a button on the steering wheel for you to activate if you see a cloud of diesel smoke belching out of the bus in front of you.

If you just hit the 'auto' button the AC will kick on and stay on. It will mix AC and hot air together to give you air the right temp, and it will simultaneously dehumidify your interior on a rainy day. But it will also lower your fuel economy.

If you hit 'auto' then turn off the AC component by pressing the 'snowflake' switch, it will use the heater to warm it up if below the desired temp, and blast the vent fans if it is above, without using AC.

If you hit "def,' it will blast both the heater and the AC through the window ducts at highest volume and temp to clear your windshield really fast. Once you can see, you'll want to shut it off and use your standard climate controls to regulate condensation buildup.

According to the manual, there is a sensor to detect pollutants...

AUC Automatic recirculated-air control/Recirculated-air mode

Set the desired operating mode by pressing this button repeatedly:

>LEDs off: outside air flows in continuously.

> Left-hand LED on, AUC mode: a sensor detects pollutants in the outside air. If necessary, the system blocks the supply of outside air and recirculates the inside air. As soon as the concentration of pollutants in the outside air has decreased sufficiently, the system automatically switches back to outside air supply.

> Right-hand LED on, recirculated-air mode: The supply of outside air is permanent

[London320d]

"Auto" controls the air distribution and temperature. It does NOT activate or deactivate the air conditioning (which it will work in conjunction with), or activate max cool or demister (which will override it).

It does not interfere with automatic recirculation, which operates independantly

[blackie]

Thanks everyone. I'm getting a clearer picture but several things don't add up:

As TYW points out, the AUC definitely has a sensor. If London is correct then after hitting 'auto', you also need to hit the AUC button to get the benifit of auto re-circ. Pity that. Can't see why the 'auto' button couldn't automatically activate this feature too.

Secondly, the 'auto' button definitely does activate the cooling (air con) function:

"The cooling function is only available when the
engine is running and is switched on automatically
with the AUTO program." from page 73 (under "Switching the cooling function on and off") in the non i-drive manual. If this is so then it would be great if it (the auto program) also turned the cooling function off when not needed, thus saving power and fuel. The manual doesn't say that it doesn't switch it off, only on: hence my question.

The manual also says: "The air
flow rate and your temperature specifications
will be adapted to outside influences as a result
of seasonal changes, e.g. sunlight or window
condensation." on the same page under "AUTO program"

The last part seems to imply that it detects condensation and will adjust for it, which would equate to selecting the demister.

A bit confusing if you ask me.

Anyone know the exact facts?

[London320d]

Originally Posted by blackie

......
As TYW points out, the AUC definitely has a sensor. If London is correct then after hitting 'auto', you also need to hit the AUC button to get the benifit of auto re-circ. Pity that. Can't see why the 'auto' button couldn't automatically activate this feature too.

The default state of the AUC button is auto. Only use the button if you want to control recirculation manually. Activating the main unit "Auto" setting or deactivating the main unit by manually changing it's settings will not change the "on/off/auto" state of AUC.

Originally Posted by blackie

......
Secondly, the 'auto' button definitely does activate the cooling (air con) function:

"The cooling function is only available when the
engine is running and is switched on automatically
with the AUTO program." from page 73 (under "Switching the cooling function on and off") in the non i-drive manual. If this is so then it would be great if it (the auto program) also turned the cooling function off when not needed, thus saving power and fuel. The manual doesn't say that it doesn't switch it off, only on: hence my question.

Hmmm Interesting... I think it may be that this is poorly worded. Since I have had my E90 It's only been warm enough to use Aircon last weekend here, and I definitely had to turn it on manually. I always leave the climate control unit in Auto.

In my prevous E46. Aircon definitely needed to be activated manually.

Originally Posted by blackie

......
The last part seems to imply that it detects condensation and will adjust for it, which would equate to selecting the demister.
.....

The way that the aircon unit works is to cool the air then re-heat it. The cooling has the effect of dehumidifying the air as cold air holds less moisture. When it is reheated to your desired temerature it is drier.

[spanna2000]

Wow - now I know how the dehumidifier effect works - I had been wondering about that for years.

The dumidified air is good in winter to keep the car and windows nice and dry. The aircon won't run below 1 degree C (to prevent it freezing I guess) and it can take some time to clear the windows in these circumstances. Of course when its a lot below 1 degree c (-10 say) then the ambient air is already dry.

I have tried running the car for a tank of fuel with aircon on and with aircon off and can't tell any difference. Has anyone actually seen the fuel economy worsen?

[wheeler]

Originally Posted by TYW

According to the manual, there is a sensor to detect pollutants...

AUC Automatic recirculated-air control/Recirculated-air mode

Set the desired operating mode by pressing this button repeatedly:

>LEDs off: outside air flows in continuously.

> Left-hand LED on, AUC mode: a sensor detects pollutants in the outside air. If necessary, the system blocks the supply of outside air and recirculates the inside air. As soon as the concentration of pollutants in the outside air has decreased sufficiently, the system automatically switches back to outside air supply.



> Right-hand LED on, recirculated-air mode: The supply of outside air is permanent

Wow, I did not know that. Cool!

[David328M-Sport]

Originally Posted by spanna2000

I have tried running the car for a tank of fuel with aircon on and with aircon off and can't tell any difference. Has anyone actually seen the fuel economy worsen?

I agree with you. Also, I cannot feel any power sapping when the a/c is active. Our E90s are great!

[AWD Addict]

Okay, I'm thoroughly confused by the manual, and after reading this thread, I'm more confused.

Put simply, how do I set my HVAC to recirc or outside air? I can't tell a difference between the settings (incl. Auto), and the lights are totally confusing. The manual says the same thing for the LED on the right or left, or I'm misunderstanding "The supply of outside air is permanent"

WTF does that mean?

[dakine]

Originally Posted by David325Australia

I agree with you. Also, I cannot feel any power sapping when the a/c is active. Our E90s are great!

From my experience, 6cyl engines now days don't suffer from the AC power loss the 4cyls suffer from (noticably anyway). My tacoma, grand prix and friend's supras, bmws, jeeps, etc noticed no loss when the AC was on. definately no 8 cyl cars either.