My central locking system just went out on my '84 190E. Now, after unlocking the driver's door, I have to reach all around from within the car's interior to unlock each door manually. After unlocking the driver's door lock, for about 20 seconds I hear an electric buzzing sound near the rear passenger-side door/seat area. Where exactly are the locations of the central locking electric pump and the actuators, so I can troublshoot the problem? If you have any additional insights on getting to them, inspecting them, removing them, and on preventive maintenance (e.g., using moly grease or WD 40 on specific areas) please include the details. I don't want to break any plastic parts, molding, or short out anything, and I do want to do a thorough job with the PM if I am going to go to the trouble of getting into the door panels or under the seat areas. Cheers!