Originally Posted by layback40 (Post 2665260)

Army,
Thats good advice.
Down here, any alts that are of the open design like you find on a car, that we have on equipment like tractors that work in dusty conditions, get the inside of their alts "sand blasted" as the fan draws air through for cooling. All the exposed wire ends up bright shinny copper. Any time an alt is off, we get the insides re-varnished by an electric motor re-winder.
We have an old scraper that is electric steer & elevator. Every few 1000 hrs of use its electric motors need re-varnishing. It runs over 400v 120 hz so any insulation break down would probably cause lots of sparks, maybe a tingle in your hands too.