Why does my AC let in outside air???
 

2001 X5 3.0 with automatic AC. I'm chasing down strange behavior for my AC (it's always done it) and I'm now realizing that MY FRESH AIR DOOR KEEPS OPENING!!! It's as if I have the AC set to automatic recirculation control, but I NEVER do that. It is always set to "recirculate" only. Do Ihave a defective computer, or does BMW do this, in spite of what I want it to do, in order to maintain "cabin air quality???" I'm about to take out the cabin air filter and stick a piece of plywood in there.

The older ones had an oxygen sensor that would open the vents if the oxygen level got low and I would assume that is probably still the case. It shouldn't open very often though AFAIK.

That might be it. There is a fan of some type that is pulling air through the little control vent. I always thought it was for the ozone generator but it could do other things. I'm going to block off the fresh air intake. It is the enemy in Florida.

That fan pulls air in for the temp sensor (and possibly oxygen sensor) The older ones stuck out on the dash so were more obvious.

When I first got my '01, it needed to have the little fan vacuumed out, then the recirculation setting worked better, after that. It's probably an overlooked maintenance item on many cars.

But if you click the recirc button twice it should not cycle anymore?

I think the vent door mechanism can freeze up on these sometimes. This was mentioned to me by the tech who I had do the evap core.

If you have access to INPA it can actuate the flaps I think, should help in diagnosing.

Very good catch...just put my shop vac on mine couple months ago.[emoji106][emoji817]

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