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Looks BMW do has some sort of sensor for toxic gases such as CO and NO2. I double it will tell bad smell though.
Here is the explanation copied from BMW web:
Automatic Air Recirculation (AAR).
Automatic Air Recirculation (AAR) protects the driver and passengers by preventing pollutants outside the vehicle from entering the cabin.
The system recognises gases in the air from outside the cabin - carbon monoxide, nitrogen oxide and other pollutants in the surrounding atmosphere. If their concentrations are too high, the system automatically switches to recirculation for a time. The air in the cabin is processed and filtered by the climate control system. Air from outside is only reintroduced when the system detects that the level of pollutants has fallen.
Yep, that sounds familiar to what I read in our old X3 manual.
On page 70, regular "Recirculation Mode - In recirculation mode, the air inside the vehicle is circulated and filtered. This prevents the unfiltered air outside the vehicle from entering the vehicle interior. We recommend switching recirculation mode on when driving through a tunnel or when sitting in traffic."
From page 71 of my manual "Automatic Recirculation - When switched on, automatic recirculation crontrols the recirculation mode automatically(DUH!). You must press the "windshield icon" MAX button if fog forms on the windows." This is seltected in the MMI: Menu>vehicle>left control button>air contitioning This should be what you were looking for.
EDIT: Just read a little more "Warning - You should not use the recirculation mode for an extended period of time since no fresh air is drawn in(so if you stink, thats on you). With the air-conditioning switched off, the windows can fog up, which increases the risk of an accident". OK, but if you have the HVAC set to AUTO, that normally keeps the AC on. Is it not possible to have automatic recirculation functioning when the HVAC is set on Auto??
Thanks for posting this. I read the same thing in my manual last night too, and I cannot extract a shred of meaningful info about how the "automatic-ness" is actually supposed to work. I would have assumed it sniffs the air and auto-switches between recirc and non-recirc as needed, but my experience suggests otherwise. (OR, Im expecting the sniffer to be more sensitive that it really is.) Another possibility I considered is that, maybe the "autoness" is mode-based, meaning it auto-switches into, or out of, recirc mode with certain combinations of other settings.) But I couldnt identify any pattern there either. And honestly, I can't imagine a reason why you'd ever want the car to automatically switch to recirc mode, other than the outside air being foul.
So, I remain stumped. Hence, the thread.
Last edited by SkiingInABlueDream; 01-24-2019 at 09:52 AM.
Thanks for posting this. I read the same thing in my manual last night too, and I cannot extract a shred of meaningful info about how the "automatic-ness" is actually supposed to work. I would have assumed it sniffs the air and auto-switches between recirc and non-recirc as needed, but my experience suggests otherwise. (OR, Im expecting the sniffer to be more sensitive that it really is.) Another possibility I considered is that, maybe the "autoness" is mode-based, meaning it auto-switches into, or out of, recirc mode with certain combinations of other settings.) But I couldnt identify any pattern there either. And honestly, I can't imagine a reason why you'd ever want the car to automatically switch to recirc mode, other than the outside air being foul.
So, I remain stumped. Hence, the thread.
I Happen to believe the auto-ness of the system, has something to do with air quality. Way back when i first got my OBD11 i change an adaptation in Air Conditioning named (Air quality sensor sensitivity) from default-medium to Maximum.
Auto-recirc is mainly for summertime use, as it makes the AC run more efficiently by running the already-cool cabin air back through the evaporator to maintain the desired temperature.
This is from the 2019 A8 manual. Since this is the most advanced vehicle in their line up, we can assume the A4 system won’t be any better than this. It’s al related to outside air temperature. Unfortunately there is no pollen sensor for outside air in our cars.
Auto-recirc is mainly for summertime use, as it makes the AC run more efficiently by running the already-cool cabin air back through the evaporator to maintain the desired temperature.
This. Recirculation recools the already cooler cabin air or dehumidifies humid outside air (to keep windows from fogging) automatically. It doesnt detect skunks or diesel exhaust.
Auto-recirc is mainly for summertime use, as it makes the AC run more efficiently by running the already-cool cabin air back through the evaporator to maintain the desired temperature.
Originally Posted by dbias
This. Recirculation recools the already cooler cabin air or dehumidifies humid outside air (to keep windows from fogging) automatically. It doesnt detect skunks or diesel exhaust.
^^ Alright, this sounds plausible. I get all the car-HVAC implications of recirculated vs outside air modes (reducing demand on the AC system for any set temp, when outside temp is high; increased risk of fogging in recirc mode; etc). An auto-recirc function that activates based on outside temp and/or high-AC-load conditions could be an effective fuel economy feature.
Assuming this is all correct, I'll consider my question answered unless someone has other info to toss in.
I think the things that threw me off were the lack of real info in the A4 manual, and the use of the phrase 'air quality sensor' in the A8 manual and the OBD11 option Bestcar17 cited.
Poor wording on Audi's part! <insert finger-wagging emoji>
I think the things that threw me off were the lack of real info in the A4 manual
The A4 manual that came with my 2018 is terrible. Certain features are sparsely covered or left out altogether. For instance, my car has a manual transmission, yet there is no mention of such a feature anywhere. If you were new to Audi and wanted to learn how the reverse lockout operated, you won’t find it there.
Here is the manual (for reference) from my car that has the Auto Recirculation checkbox option in the MMI (2018 A5 Sportback). Note where it says "AUTO Automatic Mode". Thank you to previous posts that described this mode as not auto filtering out bad smells but more-so being an AC efficiency setting.
01-24-2019, 09:42 AM
