Sorry tengleman, kept forgetting to get back to you.. If the little cable has been overstretched then it can let the indicator be off. Not sure why yours would be just stuck on S though. Try taking the end back off of the pivot, release pressure and then pull on it lightly. Should see the indicator moving. When reinstalling onto pivot make sure it is full seated. Also make sure that the cable is going under that little bendable tab and cable is within that part round cable track on the pivot area. I might be able to get some pics this weekend of our 91 that will show you the routing or have you fixed it already.
If worse comes to worse the indicator assembly is available as a separate part so you would not have to replace the entire instrument panel.