After replacing my leaking heater matrix I noticed I was getting air blow by on certain settings. The air comes out past the heater matrix, not all of the vent locations like it is supposed to. I have not figured out which setting it is yet. In looking at the workshop manual, there seems to be 5 vents inside that move to different positions to direct the airflow. If one of them is stuck or broken, can anything be done to repair them? Has anyone ever been inside one. Removal seems to require draining coolant and R134a. I still have the dash removed and have been putting off getting back to this, but I should have easier access if there are any options that do not require removal. This is on the 99SD.