2003 Heating/AC noise

I have a 2003 taurus SEL, with the automatic temp. controls. Whenever the AC or heat is on for a few minutes, and i'm driving, I notie a rattling noise coming from the passenger side near the center of the car. If i turn off the system, the noise stops. Am i correct in assuming that some kind of blower or fan isn't working properly? My brother had a 2003 as well, and I am almost sure he had the same problem, and they replaced something to fix it, we just don't know what. They also told him that it was a known issue with early 2003 models, and a recall was possible. Unfortunately, the dealer wouldn't do anything to fix mine, because the noise usually starts only after going over a rough surface or a bump. The dealer said they heard no noise when they had the car turned on in the parking lot, and doesn't know anything about it being a common problem. Anyone have any info on how I can get this fixed? (I'm not really good with auto stuff, so fixing it myself is probably not an option for me)

Thanks!
Chris

It could be something as simple as something having fallen in the vent (gum wrapper, leaf, kids toy)......not that it ever happened to me :banghead: