After marked cruise controll and speed signal
 

I am installing an aftermarked cruise controll in my 85 500 SECEuro.
The installation is so far straight forward.
Only thing remaining is the last wiring wich includes a speed signal.
The unit can use either a "VSS" (Viechle Speed signal) or a signal from a magnet switch mounted on the drive shaft.
I can not find out if my car has a VSS. I think a magnet switch could create vibrations on the drive shaft, pluss I'll have to crawl under the car.
Any thoughts

Stein

The electronic speedo has the vehicle speed output for the cruise control on the factory unit. There is a single pin in the middle of the speedo.