Radiator fan increases fan speed...
 

Hi, i've noticed whenever i drive in my condo underground parking garage after a few minutes then i go to park the car i will hear an increase in the fan noise (it actually gets somewhat loud). ambient temp is around 0 degrees c. is this a new feature because i never heard my e53 do this. car is 2009 30i

try switching off the auto recirculation function of the air intake and it will probably stop doing it...
this is normal when the car detects poor air quality such as in underground parking lots or tunnels, it switches automatically and by doing so it increases slightly the fan speed

> auto recirculation function of the air intake


Are we talking radiator fans or HVAC blower?

the fan noise came from under the hood. i dont recall pressing the auto recirculate button. hmmmm....