I would run a wire for the battery with fuse AT the battery. You can run it throught the firewall groumet and follow other comment to run it with the car wire. Just remember to put fuse by the battery, otherwise, if the wire is shorten, the wire might burn ( I saw it happening in front of me)

Good luck

Sam

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1989 300E, 152k miles
1988 300E, 172k miles


"There is nothing more expensive than a cheap Mercedes-Benz" -unknown