The 2013 model cars at least seem to be a lemon with this issue. I had this same issue at 37K miles and mercedes repaired it under warranty. 2019 64K miles and once again I have this same issue. Turn on the AC and bam it sounds like a fish is flopping around in the front end again. TWICE now this same issue same car and now I have to pay out of pocket for the repair. I wont be buying any more smart cars after this. First its rear axle, then the fan, then the axle again, now the fan again.