I have a popping noise coming from the center of the dash at key on, and when switching to and from the windsheild defrost. Everything is still working as it should other than the defrost blowing lightly when the floor vents are selected. I'm thinking that its the defrost actuator, but I'm not certian. Anyone have any other ideas as to what it could be, and would I be able to get to the defrost actuator from under the dash or is the dash going to have to come out?