Dan, Do you or does anyone have any ideas on how to make it work?

I bought 1 new combo switch and aquired 1 from an auto wrecker. All 3 combo switches gave the same results. Wipers stuck on intermitent switch works fine. Electrical schematics show that there is an interval switch or relay, also a separate wiper/relay. The wiper relay is a part sold for the 1980 300SD. Thanks Robert Mullins RAMBOB