This morning I noticed that basically no air is coming from any of my vents even though the blower motor is running fine. Even if i turn the fan up to full and set the air to come out of the upper vents, I can just barely feel any air coming out of them. The same thing happens if I direct the air to the defrosters or floor. My initial guess is that some sort of critter has built a nest up in there, has anyone ever seen this issue before?