This happened earlier today. I parked the (1999 S500 W140) car at the Dr, office. When I came back to unlock the car (with my remote), I see the parking lights flashing which is normal behavior); however, the driver side door does not unlock. I thought there may be an issue with the batteries in the remote. Tried to open the doors by inserting the key into the key-hole. I see a small movement on the latch (ie., it does not come up fully to unlock the door)..

Finally, has to call AAA to come and unlock the door, so that I could get home. However, I have to leave the doors unlocked (as I am not able to unlock the car, once it is locked)

Can you folks please let me know how I can fix the mechanical lock to work? Once I figure this out, hopefully the remote will work too.

I live in Maryland/Washington DC area. If you are aware of any good mechanics I can take the car, please let me know as well.

My cell # is 2026578770.. Thanks very much

Thanks a lot Plutoe.. What would be the part name that I need to order? Would you know please?

The vin # is WDBGA51G3XA426966.

As I mentioned, if I insert the key into the key-hole, I am able to lock this (ie the latch on the door goes down completely). However, when I try to unlock, the latch goes up partially and the door is still locked. I am thinking that some spring action is out of whack!

I also noticed that the keys ( for other door locks and the trunk) no longer work either.. I am unable to lock or unlock the rest of the doors or release the trunk using these keys on the front panel.

The W140 central locking system includes two microswitches mounted at the top of the driver's door latch assembly. These switches detect key rotation and cause the system to lock or unlock the doors. NOTE: There is not a direct physical connection between the key cylinder and the lock assembly. The assembly which includes the lock/unlock microswitches is 140-820-69-10. To replace these switches, the whole latch/lock system must be removed from the door, not a task for the faint of heart or time constrained. It seems likely that one of your microswitches is no longer closing to trigger the "unlock" request. Also: always remenber to reset the central locking controller after any work, by pulling and reinserting Fuse #11 in the rear fuse block in the trunk.