How to test a 3 speed wiper motor?

Does anyone know how to test a 3 speed variable wiper motor? My dads wiper motor on his 70 chally vert that he just got is not working and there is power going out to the wiper harness and continuity from the plug to the splice points on the wiper motor wiring. I would like to test the wiper motor to be sure that it is toast before I send it out and have it redone.

Thanks,

Brian

The factory service manual has detailed steps to diagnose. Clean the ground strap and steel grommet. Commonly when it all of a sudden does nothing the ground is lost.

Thanks, I ended up pulling the motor apart and the brushes were completely filthy as well as the magnets had rust on them. A little bit of sand paper and cleaning up the brushes and armature and the thing works as good as new.