I have a circa 1990s SL electric windlass - had some trouble with the foot switches and fixed that - still would not crank, even with the engine running. I took the thing apart, took the motor out and hooked a battery to it - spins like a top. I spun the gears and it all worked mechanically.

I put the motor back in and it works forward and reverse. Just curious why it froze up, as i am expecting it to happen next time I really need it. The insides were clean and greased. Any ideas?