I would start with re-checking all the fuses! even if they "look" good, and sometimes even if they test good with a multimeter, they can have a hairline crack that cuts the current. On my '87 300E, #5 (white) is the instrument fuse, and it buzzed, then popped when it went out.

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John

2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)

Click to see 87 300E