You see many with the #8 fuseholder position melted. That is for "blower high". In my 2 300D, I ran a wire straight from BATT+ to the Blower Speed box (above glove-box), with a 30A relay. It powers that box when the normal 12 V source wire is hot. I removed that wire and ran it to coil+ (term 85) of the new relay. Not just a M-B issue. I did the same in my 1960's Chrysler cars long ago since they liked to melt the switches in the "blower high" position.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans