What's the Difference??: two recirculate modes

[MNm3]

Given the massive heat wave, I've actually had to use the recirculate air function on my car... I have questions though.

What is the difference between these two recirculate modes?

When you press the Max * button, it turns on the recirc without the "A" in the middle. Which one does what?

[dirtyfreebooter]

This is clearly stated in the manual! One mode is auto senses bad air and switches between fresh air and recirculated air based on the sensor.

[MNm3]

Originally Posted by robackja

This is clearly stated in the manual! One mode is auto senses bad air and switches between fresh air and recirculated air based on the sensor.

I'm aware of that. But, my owners manual is back home unfortunately and I"m not going to be back there for another couple of days.

How in the world does it know what bad air and good air is? That's pretty cool actually.

[DavidZ]

I would guess it senses "particulates" in the air, like pollen, and switches to recirc. I would hope it's sensitive enough to sense diesel particulates too. Stinky.

[dirtyfreebooter]

Originally Posted by MNm3

I'm aware of that. But, my owners manual is back home unfortunately and I"m not going to be back there for another couple of days.

Just log into BMW.com and download the PDF

[dirtyfreebooter]

Originally Posted by DavidZ

I would guess it senses "particulates" in the air, like pollen, and switches to recirc. I would hope it's sensitive enough to sense diesel particulates too. Stinky.

Unless you are cruising next the exhaust of a diesel truck for a period of time, the sensor is not that sensitive (or quick adjusting), say if you drive by a truck, and then they floor it and cover you in diesel smoke it will still smell briefly of the diesel.

[DavidZ]

Originally Posted by robackja

Unless you are cruising next the exhaust of a diesel truck for a period of time, the sensor is not that sensitive (or quick adjusting), say if you drive by a truck, and then they floor it and cover you in diesel smoke it will still smell briefly of the diesel.

In my area we have tons of buses and it's not uncommon to be behind them for long periods of time in heavy traffic and their exhausts are right on the back. When this happens with my other cars I manually switch to recirc. I doubt the BMW's sensor is sensitive enough to switch to recirc in these circumstances, but hope it is... I know I could manually switch it as well but I've left it on auto since I got the car a few months ago.

[mdosu]

^i generally put it on recirc, and keep it off the "A". This way it'll make your air conditioning more efficient. Anyone notices that the car retains the cabin temperature really well?