92 Mercedes 3oosd cruise control

I have a 92 Mercedes 300sd(diesel) Car runs great, but the cruise control does not work. Fuse is good. Any idea what might be involved trying to repair this?
Thanks
Tim

does the speedometer work?

does the speedometer work?
Yes the speedometer does work.
Thanks

if the speedometer does, then we can eliminate some mechanical issues and look for possible vaccum leaks associated with the mechanism mounted on top of the valve cover, and make sure the mechanical linkage is hooked up to the governor that is mounted behind the power steering pump. if all of this is good , fuse is good, switches good, you should be cruisin' ? Has it ever worked since you have owned the car ?

It has never worked for me, but I have only owned it a few months. It is s 92 300 sd. The dealer quoted $1500.00 over the phone as the likely cost to repair. I declined.

doubble check all connections eeeespecially the vaccum stuff these cars have many functions that depend on vaccum , the cruise control system is highly dependant on vaccum