i just purchased a used one and noticed today while driving that there is a loud whirring sound coming from the front dash...off to the left...seemingly around the vents. I was thinking it may be some sort of vent issue, but when I turned off the heat, and then went back and forth between heat/ac, nothing changed. The noise can come and go, and also it stays for awhile or sometimes stops quickly! When the noise begins to stop..it sounds like a fan slowing down and stopping. But i would think that the fan would be the heat/ac, but its not...any ideas??!! Thankx!