[codefox1]

Well, one approach, after soaking it, count precisely the turns from opened from it's shut position. Yeah, probably less than two. At least that will get you started. But then again, if all the crud is on the outside, and you can get it off with, say deoxit, or gas (outdoors!) and an old toothbrush, maybe it's OK. Isolate and measure with ohmmeter if possible to eliminate short-by-crud. You can always go back to it.