1986 300 SDL Mercedes 246,000 miles Door Lock Issues
 

I have a 1986 300 SDL Mercedes and I have been having trouble locking the driver door. When ever I use the key to lock and unlock the door, I am able to unlock the door properly with the switch key. However, when I attempt to lock the driver door with the key I am not able to engage the lock. The lock’s switch turns but does not engage the cylinder to lock the door. I have to open the rear door and lock the front door manually.


Does anyone having any suggestions of where I might start. The keys I am using are in next to new condition.
Thanks,

Ron