You didn't perhap use one of the ancient spare fuses in the fuse box to replace #6, did you?

They get old and oxidized (the fuse material is aluminum or copper foil) and crack. The crack is often not visible until you remove the fuse, and even if not used, they go bad sitting in the fuse box.

You are hardly the first one to do this. At least you didn't do something drastic like replace the engine to fix a leaking hose or anything....

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!