Thank you for identifying the location of the Instrument Illumination Control Unit, the source of my problem. As I indicated in an earlier post, I had no lights on the lower center console of my 1990 300E. This included the gear selector, power window switches, and sunroof switch along with some other switches.
I traced the problem the IICC but did not replace the unit. Instead, I opened and examined the unit itself. The IICC is actually an electronic switch that powers the locations where I had not lights.
The interesting part is upon close examination of the unit, I observed that a 5 wire ribbon connector used to connect the 2 circuit boards had not been correctly installed. 1 wire was just laying unconnected near its insertion point. The funny thing is that it apparently when VDO assembled it that wire was making contact with the component that it was intended to. However over the years and 91,000 miles later, the contact was broken.
Anyway with a little solder, the wire was connected as it should have been and all is well with my lights.
I just thought I would pass this experience along