I've pulled one of the 70-1 variable switches (2nd in Slott's lineup) apart and they're kind of tricky. If the resistor part is burnt up, they're pretty much landfill. The frozen shaft might have to do with a little gizmo inside that rotates and reverses the circuit for parking the wipers. With a little patience, you might be able to get that working again, but if the shaft is broken off, I think it is hopeless.