There has always been a loud flapping noise when I crank the heat up all the way in my car, say for defrost. It is almost like a piece of paper flapping in a strong wind, but steady. I have tried but am unable to pinpoint an exact location for the noise, only that it comes from the dash somewhere. Also, my ever so observant girlfriend pointed out to me that there is a much smaller amount of hot air output from the two center vents on the car when compared to the two side vents. I did not think this was normal. Any ideas on either of these problems? Are they at all related?

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