I've got a random knob
 

So I purchased a 2002 Audi TT quattro yesterday and I've researched and researched and can't figure out exactly what this knob does, sorry for the poor video quality and what not. If anyone knows, please let me know.

https://youtu.be/F7XXCgEHz60

That knob does not appear to be from the factory. perhaps an aftermarket mod for something that was removed upon resale and the person selling it did not want to have a random hole. so just left the knob. take out the drivers side fuse panel and look inside the dash to see if it has any wires going to it. if the wires are wrapped in black cloth tape then it was most likely from the factory. if it has electrical tape or loom (or no coating) then it was an aftermarket mod try tracing the wires to see where they go. or if there are no wires then you have a free switch to control anything you connect it to!