I have an odd problem with my heat-a/c vent control, this is not the normal vacuum leak I encountered with my old jeep. All modes except the defrost/floor mode work. When I place the vent control on the floor/defrost my heat will only come out defrost, I can switch between all other vent modes and it works fine. I'm not sure where to start with this issue if anyone has any ideas or a way to fix it I would greatly appreciate it.