Central Locking Problems Still - 94 S500 Coupe

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?

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.

I recall a bulletin that the internal hose on the 95? pump was defective and could be replaced, check with your dealer!
The locking pumps that are effected are built as of (Aug94) 140 800 28 48, after chassis #A284726 they would have been modified. It seems they had a defective hose inside causing a leak. the replacement hose is available as Q480 0001. This may or not be your problem, but if you hear the pump running and nothing is activated check that. These pumps also shut down if they can not develop pressure or vacuum.

quote:

ORIGINAL: sleepwalker

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.

the one under the seat is for central locking and unlocking, backup assist rods if yagot them, lumbar, HVAC assist, and the trunk handle. The handle was moved to the "close assist pump" in a bulletin in 94 I think and is that way on a 95. the pump also handled non electric headrests, and provides the trunk release function and fuel filler door.