I wanted to do the same thing, but I honestly just used an old laptop fan, wired it to usb, (it only needed 5v) and use it for now. I'd like to make one out of a normal case fan though, so I'll keep this thread in touch too
i hate xfinity, and it's bs. Full multi city outages yesterday, didn't come back for an hr, and they've yet to give a real reason why it wasn't working. They claim "technical issues" but that's a mighty big "technical issue" for half a county to go down.