Lumbar controls W126

Hello,

I've got a set of Merc W126 seats out of a 450 SEC which I will fit into
another car. These seats have the lumbar support option which I believe to
be powered by the central locking pump. As I don't have this, can anyone
advise me on whether this system is controlled by vacuum as per most
central locking systems or by positive pressure? Also, should there be a
valve fitted in the system to hold the pressure/vacuum or does the central
locking pump take care of this?

Either I can make this work cheaply with a bicycle tyre valve, cheap c/l
pump and manual switch or I'll just do without it.


Many thanks.

Mercurious