vacuum seat lock

[Effeci]

I am a new member from Italy.Just bought a 280 Se cabriolet low grille.
I am rght now working on the backrest lock vacuum system.
Everything works and the latches block the backrest of the seat when the engine is running.
When I open one door or two doors or when I press the switch on the side panel the system does not unlock.
It unlocks only when the engine is shut off.
Another information  I need is why the vacuum element has two  connectors for the hoses.
What should be plugged into these tow connectors?

Thank you everybody for the answer
 

[wwheeler]

Here are two threads that may help you. You can find more possibly with the search function.

https://www.sl113.org/forums/index.php?topic=23454.msg167739#msg167739
https://www.sl113.org/forums/index.php?topic=22157.msg158382#msg158382

A low grille is a later car and they may have changed the system some. Not sure why you would have two vacuum ports. Mine has a spring return. A second vacuum port could be a powered return that would act along with the spring to be sure it unlocks. Your inability to unlock with the engine running could very well be a vacuum leak somewhere in this complicated system. Check the second post about the operation on the '68 coupe and see how it compares to yours.

[Effeci]

Today I got the system working.
The problem was the vacuum from the intake manifold which was too high and opening the doors or pressing the side switches was not enough to break the vacuum and make the springs to release the latches.
There is a check valve right after 5 inches the hose gets out from the manifold before it splits to the right and left side.
I placed two other check valves on the system .
One in the hose over the passenger foot place and one in the hose over the driver foot place. Both  beck valves are set before the hoses split to go the door switch and to the side panel switch.
The system now works beautifully because the two additional check valves have lowered the vacuum and the springs now can release the latches of the backrests of the seats

[wwheeler]

Great! Glad to hear it worked out.

[Effeci]

Thank you Wallace.
It is anyway a crazy and complicated system.
It would have been much more simple to have a handle on one side of the backrest of the seat to release the backrest.

[Benz Dr.]

If I recall correctly, there are check valves and then there are small throttles that are placed in the vacuum lines. These throttles have a very small hole that cuts the vacuum signal down to a much lower level. Good chance someone removed them not realizing that they're a critical part of the system. Good catch!

[Effeci]

That is why I had to cut the vacuum down and to do this I only had check valves. I do not think there is a part number for these throttles as I never seen them in any drawing or diagram of the system.

[Benz Dr.]

Later cars have them but maybe 111's use a check valve as part of a throttle system.

[wwheeler]

My '68 W111 has one check valve on the vacuum line just after it comes off the manifold vacuum port. There are many "Y"s and "T"s in the system, so it is possible that these have a "choke" point. That I do not know.

Yes, I wish I had the much simpler, earlier lever to adjust the seat back.