It's possible that the whole thing was caused by a flaky fuse. The aluminum fuses are a little less expensive than copper but you pay in other ways. All metals oxidize with age but aluminum oxides are insulators while the various copper compounds are still fairly conductive -- I don't know the numbers, we need a metallurgist's knowledge here. As you have discovered, old aluminum fuses are worthless and new ones aren't much better.

In any case, it's worth putting in a new regulator. Unless the old regulator's brushes are completely worn to nothing, keep the old one as a spare (carry it in the spare tire well with your tools). By installing the new one you'll learn how to do the job in case something ever happens on the road.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970