This turned out to be a fun little project. I noticed my wife's 90 240 reverse lights were not working. Fuses and bulbs were fine. There was no voltage at the connection in the trunk.
I unscrewed the neutral safety switch, wiped off the grease with a paper towel and cleaned the contact plates on the black part with an emory cloth. I used the same to clean the contact posts on the wiper arm. I pulled the contact points away from the wiper arm. It was easy to figure out where the grease goes--the silver plate where the wiper makes contact and the wiper post.
I noticed that the neutral start position has the smallest contact plate so that is what I did my adjustments off of. The reverse plate is a little bit bigger, and then the Park contact plate is the largest. The wiper marking was right on the money for contact with the neutral position line on the black part. You can study this when you have it apart. When I reassembled, I had to adjust the switch just a mm or so rearward for the lights to come on. I have some wear on the reverse contact plate and one of the posts on the wiper, but at the present, I was able to get this to work.
Thanks again, Art, for posting those pictures. You may have done this some time ago. It is amazing what one can find on the internet, and sites like Brickboard have been wonderfully helpful for this amateur mechanic.