Over MANY years and repetition to beat it through the thick skull,

1. ALWAYS start with a fresh battery to avoid chasing tails.
2. When electrical problems begin, start by checking EVERY fuse, again, to avoid chasing tails.

It's funny when you have, for instance courtesy lights that won't turn off, it's a blown fuse in a seemingly unrelated circuit. 1969 Grand Prix. I don't remember which fuse it was anymore.