My notes from installing my custom switch panel in the SPB show wire #49 being the key wire. In the wiper stalk connector there are 3 connectors you replace. One comes from #49 and the other two go back (switched) to the wiper motor. There are 3 terminals/wires on the wiper motor (and ground). Let's call them T1, T2, T3. (I don't recall how they are actually labeled or colored. Bentley manual shows it.) T1 is directly wired to #49. If T2 is connected to #49, wipers go slow. If T3 is connected to #49, wipers go fast. So, I put a DPDT on-off-on switch there. Middle is off, up is fast (49-T3), down is slow (49-T2). You could just use a single pole switch if you only want fast on.
