Fresh air blower question

[Mike528i]

528i 2000, I was wondering if anyone out there has the same issue i have with the air coming on at unknown times and blowing very hard. I have to turn it off then back on again to stop this heavy air flow, strange though that the led meter showing the amount of power from the fan in still at a low setting. I have changed the interior temp settings and it still does this at random. I just want the outside air to come in at a constant flow and stay low in interior noise. Is this somthing that the dealer has to set from the the computer? Thanks in advance for any info.