Mine vibrates a bit when the ac is running. Do you have the correct length belt? Benz specifies a different one for the 3.0, the 2.5, and the 3.5 for some reason. Don't know what the difference is, I'm using the one AutoZone spec'd, same as a Buick 3800.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.