I just pruchased an M20D what converted to an M20C. The overhead fresh air vent is not operating properly. After remove the headline it appears the cable has disconnected at the door. The knob side cable is connected and appears to move when the knob is rotated.  I'd like to reconnect or replace this cable however there doesn't appear to be a way to remove the water tight aluminum enclosure around the vent to access the cable termination/vent mechanism without removing the rivets that hold this