Standing in front of the car, with the hood open, look at the wheel well, you will find a black rectangle box. Lift the cover off and you will see a flat piece of aluminum, which is the 80 amp fuse. The box BTW is your glowplug relay.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member