I purchased my 2008 MCS a few weeks ago. It has 67k miles with the Automatic transmission and it also has the manual AC (not the auto-AC).

As I've been cruising down the road a few times, I've noticed the AC fan speed dropped off a bit. It's been like 110+ degrees here in North Texas, so I've usually been driving with my fan on the max high speed with the recirculation mode enabled. As I'm driving, I randomly hear the speed drop off, and the smell of the air changes a bit. It doesn't stink - it's just a noticeable change in smell and perhaps humidity in the cabin air.

On my own, I turned off the recirculate button - the fan dropped to the same speed that it previously did on its own, and that outside air (fresh air...) smell came back.

Is this normal?

 

That is normal. Both my Minis did it. From what I take it when it is in recirculate the air in the car could become contaminated. Every so often the car will bring in outside air for a short time to flush out the stale air.

 

Just a suggestion, it is not going to fix your problem but, change your cabin filter. Its something that is looked over way to much.

 

I read somewhere that owns must desgin the rec feature to let in fresh air every 20 minutes or so...yet another big brother rule..

 

Thanks everyone - I figured it was some kind of automated feature to introduce fresh air periodically into the cabin (since the air stays cold when it activates the feature), but just wanted to make sure. Thanks for the input. And yes, I did just replace my cabin air filter a couple days ago.

 

Sweet!