Is there a known issue that causes this on a 1967? Aside from old wiring, worn out motor, and lousy charging system, is there some other issue that commonly causes the wiper motor to run slowly. Like perhaps a ground issue or something like that? I dont want to replace it and end up with the same situation. I know the wiring is kinda tricky. Is there a way to jump the motor with a hot lead to see if the motor is ok and or properly grounded. ? I have the same issue with my a/c blower motor too if that helps. I think thats just a worn out motor though as it whistles when running.