I have a 1988 560 SEC and the door lock vacuum system does not work. That is I can only lock the two doors and trunk with the key. I have replaced the vacuuum pump and know it is good. There does not seem to be a signal getting to the pump to turn it on. Any thoughts or experience on this would be appreciated. Incidently, could this be a grounding problem and if so where is the world would be the appropriate grounding post??

I failed to mention that if I lock the passenger side door my radio sytem will not work????? Might this be associated with the alarm system? Anybody know where the black box is for the alarm system? and can it be simply unplugged with no other consequenses other that no alarm system, hmm?? Lee
1988 560 SEC
1983 380SL
1980 450 SLC 5.0 (Euro) for sale!

the alarm module is located under the passenger side foot well/kick panel. 10mm plastic nut holds it on. The module will say Becker and will be mounted next to the transmission cover.

Yes, this will only do away w/ your alarm.

Jonathan

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the system is set up this way. YOu have a mjor vacuum leak of failure in the system. I would start at the main vacuum supply from the engine. and then the storage canister in the fender. Or take off the panels one at a time and see if the door actuators are OK, they are all vacuum driver. Can tell you much about the alarm, but I guess this is tied into the vacuum system. As far as the radio, and the dock lock, perhaps there are some electronics involved. My 79 450SLC cental locking is vacuum operated, but the windows are electric. This part is a puzzle. Does your Euro 450SLC have a stick or auto tranny by the way?

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Al Lueb
1999 C280 54K miles
1979 450 SLC 144K miles

The 126s run a separate vacuum system for the central locking - with the pump in the boot.

Am I right in understanding you have no power to the vacuum pump or there is power but no function of the locks?

If the former, then get the power back - the ground is to the chassis, if the latter - you have a vac leak somewhere.

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1988 W126 420 SE

beware of fundamentalists!

Check out the switch /connection on/in the driver side door lock. That has to be good for the pump to get a signal to 'turn-on' to lock/unlock the doors, etc.

The pump for this system is located under the back seat and is seperate from the main engine vacuum. We have checked the sytem out pretty thoroughly on the elctrical side. Bottom line, the pump is not recieving a signal from any of the locks, ie, Driver, Passenger, Trunk. It acts as though the signal is getting lost, mabey grounded out some where OR the system is not grounded and no signal or power is getting to the pump. Based on what you guys have said I think we need to go through the whole thing again AND check both the signal and power lines to and from the pump. By the way the pump is good it has been bench tested and works perfectly. Thanks for your inputs. Lee

Al: The 1980 450 SLC 5.0 has a 4 speed automatic. This is the same 4 speed that showed up in the 83+ 380SLs and other MB models around this time frame. Thanks for your input on my 560 question, Lee

Hi,
I am having a problem with the center locking pump. How did you bench-test the pump?
thanks

For starters you can leave it in place (vacuum connected) and run 2 jumper wires to the battery (either pole/ reverse does the opposite [lock/unlock]) and see if it works.

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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

thanks, i wll try this. But there are three connectors to recieve signals from doors/trunk. The pump should verify that all OK or what?

You can leave the passenger side rear window open and lean in to do the testing. Then you can see from outside if various doors are locked/unlocked... If you hear the pump working thats a start... if some doors don't lock you know where to start looking for vacuum leaks...

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Before we ever tried to install the pump we simply tested it "on-the-bench" with 12 volts +/-. It cycles based on + or - voltage. I hope this answers your question.
My problem began after installation. There is no signal getting from the door or trunk lock to the pump. Therefore, it won't lock or unlock as the case may be. I acts like a grounding problem but we cant locate it. Any thoughts from anybody would be appreciated.

I have similar problem. I tested the pump in the car with the signal coming from actuators (doorrs/trunk) it worked fine!! but that was using a direct line from the battery to the pump. This means all signals to the little 3 poles on the pump are OK, and the main power supply to the pump is not good. I tested the plug, it has a voltage but it must be so low in current to run the pump. From that I checked the wiring diagrams for the pump and could not come up with reasonable explanation (there is connectores X30 and 48F)

Any help?

I found what could be the problem. I should have done a search on this connector earlier. It is "x48f".
thanks for the members of this site