W126 420SEL Vacuum Pump Stays On After Locking Doors

[diametricalbenz]

A friend has a 1988 420SEL and apparently when the driver door lock is actuated by key or manual lock the air pump stays running for about 30 seconds or so causing the locks to stay shut and it's extremely difficult to pull open the driver side door until the pump shuts off due to fighting the vacuum. This problem is also duplicated when the door is locked from the passenger side and or by key on the passenger side.

Is there a specific switch that times the vacuum pump in the system?