Hey guys i love the good work this forum does, this is my first post and i need some help.
I just bought a 98 c200, i have observed that while inside the car, the drivers door lock pin/button does not lock other doors.
Also from outside using the metal key to lock or unlock the drivers door, all other doors do not respond.
why is this so?
However the remote locks and unlocks all doors just fine.
I have also observed that the car has no in-built anti-theft alarm is this standard with 1998 c class

 

My 1997 has an Anti Theft and I believe even that was standard then , so you should have it. Check your fuses it could be as simple as that

 

Not sure if this is your issue, however, I had a disconnect in the central locking - as well as the electric seats on the driver's side. There is a bracket inside the footwell which seems to connect all the wiring from the door into the car. There is a track for the bracken that can be reached through a small opening in the frame, which is covered by a removable plastic plug. After removing the plug you can get a screwdriver in to rotate the mechanism and close the connections.
I had a problem with the electric seats not working , nor the door lock working. I rotated the connection on the bracket and - they started working.

 

thanks bagelsjustbagel, i've checked and double-checked the fuse boxes, all the alarm/central lock fuses are intact, there is no alarm horn in the hood either.