I am still unable to get the central locking system in my 94 S500 Coupe to work. Have read all the posts to no avail.I replaced vacuum pump located over rear drivers side wheel well. Fuse is good, there is power to the unit and upon closing the trunk I can hear the pump power up. None of the doors, trunk or gas lid will lock or unlock when the key is inserted and turned into either door or the trunk. Does anyone have any suggestions as where to look next? Any thoughts at all? Thanks in advance for your help.

 

have you checked for leak?

 

No...can that be done without some kind of special equipment?

 

you can feel also if the pressure and vacuum is sufficient enough to push or pull the locking element.

you may start from the trunk lid lock for it is more accessible.

 

OK...will one leak cause the whole system to malfunction?

 

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Can you give me more specifics in how to check for a leak?

 

One more question...I was reading on another forum that the central locking vacuum pump on the 140 is located under the right rear seat and that the pump that is accessible from the trunk over the left wheel well is for the assists. Is this correct particulary for the Coupe? If so, I may replaced the wrong pump...THANKS FOR YOUR HELP!!

 

very true!

the one on the rear left inside the trunk lid is for door closing aid, back-up assist, and trunk lid handle.

under the rear right seat was that PSE pump for central locking.

 

Wow...I wished I had understood that earlier in the game. I will post a status report as soon as I can remove the pse pump. Any tricks I should be aware of for getting under the seat before I start? Thanks.