Use tweezers to place the spring arm on the lower side of the post and tension the lever.

Place the long spring arm on the left side of the mirror pivot.

Check proper function of the mirror by moving the bottom arm of the lever back and forth. The mirror should rest in the upper position but be able to move up and down.

If using a 3D printed replacement part, remove the tensioning spring and temporarily install the green gear Turn it counterclockwise through the entire mirror cycle. There should be no binding of the gear at any point. Adjust the drive lever as necessary until it moves through the entire cycle without resistance.