My 64 cutlass has 2 spd wipers they work except they won't shut off the only way to shut them off is to unplug the motor it's not the square type in all the catalogs it's round like later year motors has anybody seen this and how do i fix it

 

Check to see that the motor/ housing is getting a good ground. There is a copper strap on one of the rubber isolator mounts that grounds the body of the wiper motor to the firewall. If the housing deos not have a solid ground, the motor will not shut off.