When I bought my 300SD 15 years ago, there was a cell phone mount on the passenger side of the console. Presumably this means there would be wiring, but I am NOT electrically inclined to understand what's what.

Any idea if 126's had a similar wiring setup ? If so, I will get one of my electronically adept friends to work on this...

This is an excellent idea!

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Mine: 1987 MB 420 SEL - 66K (Dec 2019)
Mine:1991 MB 350SDL - 244K (Aug 2011)- Totalled 9/14/2016
Mine:1981 MB 300SD - 326K mi (July 1997)-sold
Wife's: 2008 MB C300 Sport - 110Kmi (April 2009)