'93 tach/cruise don't work

I recently bought a 1993 300D (had an '83 & '84 before), and the tach and cruise control both don't work. I have rebuilt the fuse box and replaced the over/volt relay with no results. I have read the cigarette butt posts, but don't see the cylinder mentioned in those posts, and suspect the system has changed from the mid '80 models. The tach and cruise control both get their power through the same fuse, and I am wondering if there is a common connector that often fails? Thanks for any help.