So I was driving down the highway tonight with the window down and started to hear a noise that kinda sounded like a rattle or more like an in window a/c unit in your house makes, but louder, so I put my window up to better hear this sound, and the noise stopped. Put the window down, noise started again. Repeat. Repeat again. I haven't looked at it yet, since this happened right around midnight, but I was hoping for any ideas anyone may have.

After I played with the window, I played with the hvac controls, and it seemed like the air coming through the vent was cold, much more than it was before this noise. After cycling through each selection, it didn't make a difference. If the window is down, and I'm driving at 65 it makes this noise. So on the exit ramp, I put the window down and at like 45 mph the noise wasn't there.

I'm thinking I'm gonna check the blower fan first, and see if maybe one of the blades is messed up. My line of thinking is window down sucks air through the hvac system, spins the blower fan, drags broken fins inside the housing, thus the noise, but thats the only thing I have come up with so far. I was running the blower on the coldest setting, but only on vent, not a/c...

Anyone have any ideas?