I changed my tail light last night based on instructions I found here.

I removed the round cover inside the trunk to access the bolt to remove the tail light. When I took off the cover there was a "ring" thing clipped in there that had a wire attached that went behind the carpet. I can't recall the colour but it was bright.. red or yellow.

Anyways... anyone know what this is for?

(2005 A4)

 

In your trunk? or on the light? If it looks like a little ring and has a wire attached to it and is on the gas tank side, it is to pop open the gas tank flap.

 

It IS on that side... I bet that is exactly what it is... probably a backup in case there is no power for the auto locks... Thanks

 

Correct it is incase the power lock goes out. Do not let it drop down the side.