Isuue with new vacuum trunk element 77 450sl

[miaminikko]

Hi,
My trunk element had a hole in the diapraghm. I ordered a new unit VDO/siemens.
When I installed it the trunk would not open ( even with the key). I managed to open it eventually and debugged the problem. The new unit does not snap into position in open. It wants to sit the an intermediate position. This causes the trunk lock to not open. ( bad)
The new unit snaps to the closed position like it should and with vacuum to the open. But if the vacuum dies it spans to intermediate , which could jam the lock
I checked the old unit and it snaps from closed to open. ( and never stays intermediate)
I am returning the new unit
Please help, anyone seen this before, how should these elements work.?
Nick

[abe g]

I had this problem on my 77 450sl. Same thing with vacum lock on gas lid. Best not to depend on these on older cars.. Disconnected vacum and open trunk with key (or lock yourself out). Good luck, Abe G