ok. i found information on our vaccuum door locks. i realizes it changes polarity in order to lock/unlock door. here what i found:
Found mostly on Mercedes Benz vehicles, the movement of the door lock actuators is controlled by a central vacuum pump. The switch changes polarity on a single wire that may rest at power or ground depending on the state of the door locks. You can duplicate this with at least a 2 second pulse. If the alarm or keyless entry you are installing does not have a 2 second or longer duration option for the door lock outputs, do not use this diagram (it will not work unless you incorporate a timer into this circuit).