Good ideas.
I suspect the OVP too.
Its been sitting somewhere since Feb 2010 when the tags expired, and as the battery is new looking yet flat, I bet its been jumped... surefire way to kill an OVP.
Only other thing I saw that was wrong with it was the parking brake... the button is stuck in and so it wont stay on when pulled up...

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2009 Mercedes ML320 Bluetec