It stopped working and when I tried to figure out why it was mostly clear: it couldn't move because of some duct tape. I then removed the clog with tape but found the motor had died and the fan would no longer run. (Afterwards, I happily disassembled the fan with a screwdriver to figure out how the motor might have failed. I saw no evidence of burning or melting, and my investigation yielded no answer—just a long puzzle.)