I can vouch for the wipers on a topless Spyder. I ran that way for a few years before I had a top. They DO work, even in the pouring rain they help vision. That and a towel to wipe the inside makes it survivable. Definitely not fun or comfortable though.
When I got my car the wipers had no park feature, but Hi and Low worked(only 2 wires to the switch). I played with the wiring and took it apart just like Carlos and popped a bunch of fuses until I figured it out. Mine is wired like the diagram I posted above. I cleaned it, re-greased it, and re-assembled. Works great now.
Carlos, say thanks to yourself and don't over analyze it. Accept that it works!
I am also working on a top design, but similar to the Boxster Spyder design, with upright rear window, plexi side curtains, and cloth flying buttresses to the rear clamshell. The top should roll up flat and store in the front trunk with no frame to speak of, plus three flat windows.