Originally Posted by parios
We’ve noticed an intermittent whistling sound emanating from the mid-passenger side when traveling above 50 mph, when air temp. is warm (70-80 degrees F) & is especially noticeable on rough or bumpy road (e.g., crossing a bridge). The sound lasts about 5-10 seconds then slowly dissipates only to return later at another bridge/bump. However, it does not occur at every bridge/bump and a few times occurred when there is no bridge/bump. The sound is similar to a muffled tea kettle whistle. Airstream support said to contact MB dealer that services Sprinters.
Since the sound typically happens after you hit a bump, I'm tempted to believe that something isn't shut tightly. And since you'd get a message on your dashboard if a door wasn't shut tight, that leads me to suspect one of the tip-out side windows is the culprit.
I've driven thousands of miles with the MaxxFan vent open with no whistling sound, and accidentally driven with the bathroom vent open for hundreds of miles, with no whistling sound. I don't think it's your vents.