I just looked for the thread announcing his passing and while it comes up in a search, it can not be viewed, so I assume it's been moved to an admin only section.
When you're getting just one speed does the motor go through it's full park cycle or does it just shut off wherever you shut it off at? That's usually one of two problems. Either it's a 2 speed switch with a 3 speed motor OR it could be ground to the switch. The motor will act the same on both scenarios. Do you have the PN off the switch? Have you bench tested the switch? Let's start with does it park when you turn it off, I get the one speed but you don't mention if the motor parks.
http://www.passion4mopars.com/Testing-and-Wiring-a-3-Speed-Switch_b_46.html
http://www.passion4mopars.com/How-T...ece-NevilleGeneral-Industries-Motors_b_4.html
If you want to try to rule out the switch you can try a lead with alligator clips or whatever and go from the switch to another portion of the car where you know you have good ground and see if the motor acts the same?