If there is no electric to the switch then it is unlikely the wipers are electric. Is it possible that you are mistaking the vacuum line for a wire? It's pretty dark up in there. If it really is a wire then if you put 6 volts to it and you have a good ground the motor will either work or it won't. It is likely at least 40 years old and the grease in it will be hardened, so it needs to come out for a good cleaning anyway. I picked up a motor out of a '36 ford at the salvage yard and gave it a good cleaning, miracles do happen with old electric motors.
