When you lock the driver’s door with the key, the pin in the solenoid goes down and an electrical switch gets activated so that the vacuum pump knows what to do...this is electrical.
When you lock the car from the trunk or the passenger's door, the vacuum pump is controlled by the lock you are using at that time and the drivers door has to be locked by the vacuum pump and connected vacuum line...this is vacuum.

The functioning of the electrical switch in the driver’s door solenoid/diaphragm has nothing to do with the vacuum part of that solenoid (or the lines towards it).

I hope that this Dutch information was clear enough (don't know the right words to use).

greetingz,

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)