If the fuse for the radio keeps blowing when you turn it on don't assume the headunit is the problem, there's the tuner computer and in the W124s case an amplifier under the seat to check too.

-Jason

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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.