As the title says I have a 93 Legacy Wagon, automatic, 154k miles, and I was wondering if anyone else might have had this problem and could point out where I should turn before I start ripping the dash apart.

So when I use any vent button and then use the off button I can hear this clicking noise that sounds like one of the flaps trying to close over and over again. It's quite loud and annoys me so I usually just hit the vent button and it stops. Thanks for looking into this and any help one would provide.

I have worked with various cars with various vent issues, but not so much with Subaru. From what you describe, one of the vent closures is getting hung up. I don't know if your system is electrical or pneumatic for flap closure. I would suggest you try to pin point the exact source of the sound, then see if you can remove anything to see what is making the noise. Could be something fell into the vent to cause an obstruction, and the noise upon closure.