[agentorange]

I wonder how much of this is tied to AC compressor load and maximizing economy. By switching to recirc when the actual cabin temperature and demanded temperature differ by too much, the time taken for the compressor to run at full bore is reduced, lessening the load on the engine and improving economy. I understand that many have a fixation with "fresh" air, but living here in the desert I can assure you it is rarely "fresh". This counts double in any city I've visited.

[Marcelo Ribeiro]

4 people found dead inside a G20 BMW in Brazil after stopping for resting inside the car.

Asphyxia due to carbon monoxide poisoning is the main suspect for the cause of the deaths, according to the Police.

https://noticias.uol.com.br/cotidian...llon-em-sc.htm

[Billfitz]

According to the article there was a modification made to the car that allowed exhaust to enter the cabin. Sad, but it has nothing to do with the subject of this thread, and for that matter this is not the G20 forum.

[Salty B.]

Originally Posted by HighlandPete

AUC sensor can lose sensitivity over time, I'd suggest that mode of failure would leave the system open to 'outside air' more often.

Original (2001) AUC sensor in my E53 threw a code. After I replaced it I did notice exhaust smells from others go away after a few seconds, just like it's supposed to do.

So they do eventually fail with age. No idea how long it had been dead as I bought the X5 last June. I never would have even known it existed if I hadn't seen the code (found while clearing others that kicked on the CEL; the AUC code would not by itself).

[22Black]

Originally Posted by JeffHou73

This is the first I have seen this entire string but find it very interesting. I have a 2020 M340i and last year, I began having some issues with either mold or moisture building in the evaporator - just getting some musty air...but still cooling well. All that seemed to resolved itself over time. HOWEVER, along the way, I observed the exact problem you have outlined in the initial post of this thread. The system does ignore the fresh/recirc/auto button ANYTIME the A/C is on, in which case it is always in recirculate mode. Aside from the sound of the air never changing, when switching modes (with A/C on), you can actually see the primary flap underneath cover the secondary battery located in the engine compartment, in front of the passenger. In fact you actually see the incoming side of the cabin filter. The ONLY way to get that flap to open is to turn off the A/C and then set the mode to "fresh air". You definitely hear and feel the air speed slow down in the cabin. If you then switch it to "recirculate", the A/C comes on automatically (which is crazy) and the air speed speeds up. THEN, if you turn off the A/C and don't touch the mode button for the air, you can have recirculating air without the A/C on (although I would never recommend it). However, you cannot have the A/C on in fresh air no matter what you try.

I actually met with a factory engineer about this here in Houston and, in effect, won a bet. he assured me the flap would be open if I put the switch in fresh air mode with the a/c on. When he saw that did not occur, he shook his head and was in somewhat disbelief. The on thing he did tell me but could not confirm was that there is more than one flap and just because we couldn't see any other flaps, he tried to assume there was still at least one flap keeping fresh air moving when the A/C was on. While this may be true, I'm convinced I will never know this for sure. The fact the air speed doesn't change convinces me, there is ni fresh air being coming thru the cabin filter when the A/C is on...which is 98% of the time in Houston. This explains why, after 3 years, my cabin filter still looked like new. Although, I did replace it anyway for good measure. Anyhnow, just wanted to share my story. The originator of this thread raised some good points and good he persisted in getting some feedback. BMW does do some crazy things and it is amazing how few people - including technicians and field representatives still do not understand about these cars!

Thanks for listening and look forward to any feedback or input any of you may have.

Hey, how were you able to meet a factory engineer on the issue? Did he have any answer as to why the flap is not functioning correctly?