said by robbin:
Not sure what it takes on your fan to get to the damper but I would recommend checking it.
Diagrams are in the PDF spec sheet and installation manual at this link:
Based upon the diagram, it looks like the damper is enclosed in plastic housing that clips to the exterior surface of the metal frame. If the o.p. has access from the attic, it will be be easy to pop it off and check it. If no attic access, then it might be possible to see from the interior of the box, but I can't tell from the diagrams.--
nohup rm -fr /&