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X3 F25 (2011 - current)
The latest X3 brings some added style and some new features to the BMW SUV family. Talk about the new F25 now!

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  #1  
Old 10-04-2013, 11:10 AM
RhoXS RhoXS is offline
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Auto A/C Recirc When Pollutants Sensed

I would like to accurately understand the exact function of the A/C recirc button.

When the left light is lit the manual (2011, P104) states " ... a sensor detects pollutants in the outside air and controls the shut-off automatically.". I interpret this as meaning a sensor will force it into recirc mode when it detects some sort of pollution. Exactly what is it sensing with respect to "pollutants" and how does it do this?

I assume auto mode also just allows the logic to switch to recirc mode when the outside air temp is too high for efficient cabin cooling. But, this statement in the manual strongly implies that the system will only go into recirc when it senses "pollutants".

Last edited by RhoXS; 10-04-2013 at 12:09 PM.
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  #2  
Old 10-04-2013, 11:58 AM
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gfeiner gfeiner is offline
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Auto A/C Recirc Whe Pollutants Sensed

I have wondered about the about the same thing. I think BMW embelished that description. They make it sound like they equip the AC system in their cars with Mass Spectrometers.


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  #3  
Old 10-04-2013, 12:08 PM
RhoXS RhoXS is offline
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Quote:
Originally Posted by gfeiner View Post
They make it sound like they equip the AC system in their cars with Mass Spectrometers.
Wow! My thoughts exactly and that is obviously not the case.
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  #4  
Old 10-04-2013, 12:52 PM
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Drewsky Drewsky is offline
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The sensor is a hydrocarbon gas detector. You dont need a full-on mass spectrometer for this, they are built pretty cheaply and inexpesively. I just went searching through my computer for the document that talked about the sensor on my e46 (it had one too) but I can't find it. It works pretty well though, the recirc "flap?" inside the dash makes it evident when it changes and pretty much like clockwork when I stop at a light amidst cars, I can hear it close me to outside air.

Edit:

Some light googling found some tidbits too: If the AUC II sensor detects an increased level of pollutants in the environment from spark-ignition and diesel engines, the IHKA control unit will automatically switch to air recirculation mode.

Last edited by Drewsky; 10-04-2013 at 12:58 PM.
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  #5  
Old 10-04-2013, 01:34 PM
02420X3 02420X3 is offline
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I noticed that the AUC II wasn't effective at detecting the dead skunk near a traffic light where I often stop on the way to the office. I'll work on dropping back a car or two...
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  #6  
Old 10-04-2013, 04:13 PM
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Drewsky Drewsky is offline
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Originally Posted by 02420X3 View Post
I noticed that the AUC II wasn't effective at detecting the dead skunk near a traffic light where I often stop on the way to the office. I'll work on dropping back a car or two...
Be behind an old car pre-catalytic converter at a stop light and that recirc baffle slams right shut! lol
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  #7  
Old 10-04-2013, 11:55 PM
RhoXS RhoXS is offline
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Quote:
Originally Posted by RhoXS View Post
I assume auto mode also just allows the logic to switch to recirc mode when the outside air temp is too high for efficient cabin cooling. But, this statement in the manual strongly implies that the system will only go into recirc when it senses "pollutants".
So, will the system also automatically go into recirc mode when needed for cooling?
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  #8  
Old 10-05-2013, 06:36 AM
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Drewsky Drewsky is offline
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Originally Posted by RhoXS View Post
So, will the system also automatically go into recirc mode when needed for cooling?
Not unless you push the max button
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  #9  
Old 10-05-2013, 07:18 AM
TerraLvr335i TerraLvr335i is offline
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Whatever it is, I find it works pretty well. On both my E90 and F25 it pretty much always prevented exhaust and similar smells into the cabin.
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Old 10-05-2013, 09:47 AM
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Liverman Liverman is offline
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Originally Posted by Drewsky View Post
Not unless you push the max button
Or push the Recirculate button twice to engage Manual Recirculation. Right LED near the "M" lights up.

Your temp setting and fan speed stay the same. With Max button, the fans goes on max and the temp goes to min as well as blocking outside air.
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