The ornamental design for an automobile back light, as shown and described.
FIG. 1 is a perspective view of an automobile back light;
FIG. 2 is a front view thereof; and,
FIG. 3 is a side view thereof.
The broken lines are included to show environmental structure and form no part of the claimed design. The drawings and descriptions represent the left side embodiment. The claim is also for a mirror image right side embodiment.