Im sure the buzzer and starter have nothing to do with each other, but is odd that the starter wont work unless the buzzer is working.
Forgot to add that there is not sign of drain when key is in starting pos. If the starter was gone it would dim dash lights showing a drain. And I also have never had the replace a starter in any of the Benz's I have had over the years. Will have a look at the grounds over the weekend.

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