I have a 1986 190D as well.

After the third time going back to a repair shop to have my radio reset, I finally pulled out the stock radio and put in an aftermarket replacement. Disconnecting the battery will disable the stock radio, so any time you need to do electrical work, it's going to happen.

I do really like the car, despite its idiosyncracies (sp?).

__________________
MB 1986 190D in my past
MB 1987 300E on the street
MB 1994 'Smoke Silver' E420 in my driveway
1999 Mazda Miata in the fun stable
1964 E-Type Jaguar Coupe- Sold
1970 E-Type Jaguar Coupe- Sold
1968 Corvair Monza Conv. with Turbo Transplant- Sold
1986 Merkur Xr4ti- abandoned
various mundane American autos

If I'd known then what I know now...

Hell, I'd probably still have done it anyways.