Door lock
 

Key will not open or lock the driver side door on my 1993 190e 2.3,
but works on trunk and passenger door. Help.

Are your keys badly worn? Have you been experienced trouble with the drivers door before it stopped working?

If you do a search on ignition locks you will find that ignition tumbler is a common failure on the w201. I don't know for sure but maybe the same goes for the door tumbler?

how easy does the lock turn? if you don't feel any tension on it the shaft for the tumbler is broken.

How long have you owned the car?

Peter