Inside your driver's door you will not find an actuator. Instead, there is a master vacuum switch that controls the actuators in the other three doors. In this picture, it is shown with the two Phillips head screws that hold its bracket in place already removed.

When the solid yellow line that you have been testing under the hood enters the firewall, it continues on and passes through a rubber tube between the vehicle's body and the door.

Once inside the door, it connects to the center vacuum connector on the main vacuum switch.

Steps 8 and 9 will include disconnecting vacuum lines from the switch. To make this easier, the switch should be detached from the door. The door pull must be detached before this is possible.