What? My car has a rear view mirror wire harness?

[Let it snow]

I have an auto dimming/compass mirror from my 02 A4 that I would like to install in my 05. I found the complete wire harness in my 05 tucked up top in the roof neatly taped to other wires from the factory. So at my excitement i plugged in the mirror and started the car. No power to the mirror. I have read a few articles about retrofitting a mirror and running a whole new harness but nothing about if the harness is there from the factory. Do I just have to recode the CECM to power the mirror? Or maybe this harness just leads to nowhere from the factory. I am only trying to have rear mirror compass/auto dimming functions, not side mirrors. Any input greatly appreciated.

[customa4]

Check out this thread. Click From what I gathered, skip to step #5.

[Let it snow]

Check out this thread. Click From what I gathered, skip to step #5.

Thanks customa4. I just read through the thread. I guess what i don't understand is if the wiring harness is there, why do you have to tap into a switched fuse for power? There must be a way to apply power to the factory installed harness the OEM route. I do not mind splicing it just seems wrong to have a perfectly good factory installed harness and yet have to pull power for it. I guess I will dive deep into the schematics and donor car to try to figure out how Audi supplied power to the mirror without using a splice. If any one knows the answer let me know. Thanks.

[diagnosticator]

The mirror wiring only runs from the overhead location down to the left kick panel wiring connection center under the panel. You need to connect the mirror wiring to "15" switched power and ground. This is because the factory did not connect the mirror wiring from the left kick panel up to the roof, to power or ground.