I bought my W123, 280E '86 Mercedes, 2 weeks ago. At that time the central locking was working. I could hear the fuel flap and boot locking. Now it doesn't work at all. The fuel flap stays open, and the boot doesn't always lock.
Any help with this??

 

On the Diesel 123s I would say it is a Vacuum leak in the system. But, I am not sure if the gas powered Cars have the same system.
If it is a vacuum issue I do not know what creates the Vacuum in your system; is there an Electric or Mechanical Vacuum Pump? Or, does it just use the Manifold Vacuum and there is a Vacuum Resivoir to store it?

 

I have my central locking system completely disabled.

Once this starts leaking it's quite expensive to maintain.

I've had my fuel door unlocked for five years now, and nobody ever took a swig.

 

i have spent lots of money trying to bring back the original air operated locking system of my w123 300d-t but all was wasted as air seems to leak away somehow, so i decided to convert my locking mechanism into an electric type with alarm and remote, this way it is more convenient in entering the car especially if its raining or your hands are occupied carrying stuff and you cant get hold of your keys and trying to speedily insert in the keyhole. so for convenience and practicality convert to electric locking

 

It is a fairly easy system. Vacuum is supplied by the inlet manifold, with a resevoir in the boot (Under the rear screen on top of the Fuel tank.

Yellow (Black stripe) supplies vacuum, and under the drivers seat (In front of) if you lift the carpets, you will see the links. Yellow with Greeo opens, and yellow with red locks.

In your case, start with the vacuum unit at the fuel flap. Remove the polastic cover in the boot and check for vacuum loaks. If it cannot lock at all, check the one way valves in the engine compartment. (3 valves - yellow, next to the vacuum booster)

 

is something like this what you have?

could this be installed on a 300 series?

 

I would check the Vacuum Hoses/Tubings under the Hood first to be sure they are not cracked or disconnected.

 

What do you mean by the "rear screen"? I bit by bit get parts of the vacuum system replaced on my 300D but suddenly the locks quit, which has made me go under the hood looking for anything that might have come disconnected. I would appreciate you telling me where the rear screen is -- oh, do you mean under the rear dash under the rear window? How do I get under that dash?

Thanks!

Connie