Why does motor comes on but brush head does not move

I have this issue as well.

The tear down guide doesn't go into the mechanical portion at the head of the brush.

I have mine open and there is an opening on the back inside that allows me to see some of the gears and they look functional. I can't figure out how to get in further to find the malfunction. Specifically, on mine, the metal 'pin' only vibrates. It is missing the up-and-down motion I recall from before.

I guess I can't add pics to the question as I'm not the op?

@scottbernardis

Post your comment as a new question on ifixit. That way you can add images.

Here's how to do this 在已经存在的问题里加入图片. It is the same procedure for a new question.

If selecting the same device as shown on this page for your question then your question will also be linked to the device, (see where it says "6 questions View All" in the device box, top right of this page). If you click on that you can see what others have asked about the device and also what answers there are.

Moderator.