Interior noise inside 2Door Tahoe???

[slam59]

I have a 1999 2door Tahoe and I have a noise that comes from where the passengers feet rest right above them. Under the glove box there is the black plastic box that looks like thats what brings in the heat or ac into the vents. It sounds like the door that opens or closes depending if you are letting in outside air or closing it to not let outside air in opens and shuts on its own. I will hear a sound that seems like it slams shut kinda loud and sometimes it's a lot more quiet than other times. Also hear tapping sounds that are like 3-5 seconds apart, thats how it started. Kind of a knocking sound. And also hear like a faint sound of humming like a electrcal motor noise. Could it be that the motor that opens and closes to let or not let outside air in is going bad? Thanks for any info or help guys.