Early Variable and Single Speed Motors... The Same?

Transform into what? Lol! Just playing.

I had mine (variable speed wiper)rebuilt by an alternator and starter rebuilder. Did a nice job. Plugged it in and it did the same as yours. After swapping out the motor twice because all electrical (wiring and what it did wire by wire) was good… I found the ground on the switch was not good. The dash board was repainted and prevented the ground from making contact (sorry 1966) once it was cleaned it worked fine, did not stop and was quiet as a church mouse. I hope yours is as easy of a fix.