Motor winding insulation varnish touchup

I removed the windings on my Alternator to replace the front bearing. I managed to nick the insulation varnish a few places on the windings. The wire is fine but bare metal is showing. Can I just touch up with regular wood varnish? I think it will probably be fine with no insulation there since it is only 12 volts and not near any other uninsulated bits. but I want to be safe and also keep the good varnish from getting water under it and starting to peel or go bad.
Bill D.

Bill D said:

I removed the windings on my Alternator to replace the front bearing. I managed to nick the insulation varnish a few places on the windings. The wire is fine but bare metal is showing. Can I just touch up with regular wood varnish? I think it will probably be fine with no insulation there since it is only 12 volts and not near any other uninsulated bits. but I want to be safe and also keep the good varnish from getting water under it and starting to peel or go bad.
Bill D.

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You might get away with a few coats of polyurethane wood varnish but the stuff on wires is baked on and capable of handling the high temps found inside motors and alternators. Voltages can spike a lot higher than the regulated 12 volts so it's essential to get it right. Silicone is high temp and has high breakdown voltages as well as being flexible enough to withstand vibrations, you do a lot worse than use a neutral cure silicone on the bare parts. Epoxy would go jelly soft with the temps found inside an alternator running at full load so I wouldn't use it even though it's a good insulator.

Glyptal!

Varnish is fine, nail polish is fine, oil based paint is fine.

Motor winding insulation

I just might take it to a motor shop and have them dip it and bake it. Then their aint no problem.
Regards Walt...

Standard baking varnish is baked at about 265 F, at which point it is also soft. Standard procedure with wrapped field coils is to heat the coil before mounting it so it will deform to fit. Whether you need to touch up the windings depends on where the nicks are. If they are not near anything else, the only issue is corrosion. I have never measured the temperatures in auto alternator windings, but a standard repair on motors and generators is a solventless polyester. You are not going to have very high voltages as long as the alternator is connected to a battery because it will absorb them. Krylon sells a red insulating varnish in spray cans, part number 7004, which probably is the simplest solution.

Bill

I would recommend a two-part insulating compound for electrical jobs.
Call DuPont. They can make a recommendation. I would not worry too much
about corrosion since the windings are most likely to be copper.

The cheap way out would be nail polish.

Wow! It's just a feaking alternator! If the copper is not damaged, then it cannot possibly be shorted. Put it back into service, the windings will NOT be the first part to fail, even with a good scrape.