1991 300D 2.5 Turbo, 125K

I had some trouble with my Central Locking system since I bought the car:
Sometimes, unlocking the passenger door, won't unlock the driver door. Also, if I lock the passenger door, sometimes the driver door wont lock automatically (I have to go around the car and lock it). Unlocking the trunk often wont unlock the driver door. I tried to find a pattern of behavior but I didn't manage to.

A few weeks ago the trunk lock stopped working with the power system. I have to manually lock/unlock the trunk.

Any ideas?

Thanks
Andreas

You probably have a vacuum leak in the line to the driver door or the driver door has a leaking solenoid. The power lock system is partial vacuum controlled and partial electrical. The solenoids of the two front doors and the trunk have an additional electrical switch to control the vacuum pump so that all other doors get (un)locked.
The line or the solenoid to/in the driver door is probably leaking.
Do you have to (un)lock the trunk manual all the time or is there any chance that you locked it once and therefore have this (un)locking "problem"? The trunklock can be locked manual after which it does not unlock with the power lock system...

greetingz,

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)

I will check out the driver door solenoids. I have only done minor work on this car (I usually take it to the shop). I did work on my previous car (85 300ZX), and i think its time I get the toolbox out and work on my 300D.

The trunk always need to be locked/unlocked manually. It behaves like its completely disconnected from the power system, so I have to go and lock/unlock it every time i need to use it. It used to work fine, this problem only started happening 4-5 months ago ..

sure is fun to watch all the locking nobs go down when it's working right.....

William Rogers.....

Ok, Spent some time on it this weekend. The trunk lock was not working with the power locks because it wasnt connected to the diaphram (is that the right term ? ). If it wasnt for this forum to give me enough self-confidence to look it up myself, I would have probably left it like that!

Still though ...
I played around with it a little bit and the behaviour is almost consistent. Locking and unlocking the trunk, locks and unlocks all the doors but the driver.. But if I put the key in the drivers door, I can lock/unlock all the doors. If I had a leaking solenoid or something, shouldnt the driver door not be able to lock the other doors ?

When you lock the driver’s door with the key, the pin in the solenoid goes down and an electrical switch gets activated so that the vacuum pump knows what to do...this is electrical.
When you lock the car from the trunk or the passenger's door, the vacuum pump is controlled by the lock you are using at that time and the drivers door has to be locked by the vacuum pump and connected vacuum line...this is vacuum.

The functioning of the electrical switch in the driver’s door solenoid/diaphragm has nothing to do with the vacuum part of that solenoid (or the lines towards it).

I hope that this Dutch information was clear enough (don't know the right words to use).

greetingz,

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)

Your dutch information was extremely clear and I do thank you a lot for it. the complex world of solenoids and electricity underneath my door panels, suddenly makes sense.
By the way, I cannot speak dutch, and i take it that you cannot speak greek, so lets use English to communicate !

I guess I will be pulling the door panel out this weekend to inspect the solenoids and all!

thanks again !