The wiper switch on my 65 mustang is broken and im trying to get it replaced, it never worked when I started restoration and when I went to get a new one there is a 2 speed version and a single speed verison. How do I tell what kind I need without being able to know how the old one operates

 

The one speed has two positions the 2 speed has 3. On, Low and high. Play with the switch and see how many positions it has.