Time and time again I see vettes that have weird problems and after all these years owners are not checking for damage due to the battery leaking acid not only seeping into wiring harness but also vaccum hoses, splice packs and the electronics like the PCM and TCM

You simply cannot wash this off, many times the acid has seeped in over time so it should be a normal practice to look for the white coating is a clue acid has gotten onto parts that will cause long term damage and weird electrial issues.

These images are from 3 different vettes so it is a common problem.