Here is the explainations:
1-losing up the stopper and bring it to the expecting stop area.
2-use small flat screwdriver or test pen to turn the left or right direction switch (2 times).
3-Now wait for the motor to start calibrating.
4-When the motor (damper) begin to move and near to stop area you must prepare with screwdriver to tighten back
the stopper.
5-At the moment the damper is fully closed quickly tighten the stopper and then you will see the damper will back to
Fully open position.