I have a 2004 a3. The front speakers have the Bose logo on them. There is a sub and amp in the boot.

these are the standard connections coming out of behind the stereo:

 

Just bought a Connects2 CT20AU11 harness adapter to attach an aftermarket stereo:

Plugged everything in, no power to the stereo. Nothing happens when ignition is turned.

 

I have scoured the internet and there are SO many different opinions for what adapter/set up is needed. 

 

Can someone please please help me? I just want to know exactly what harness/adapter is needed and be able to attach my aftermarket stereo before I pull all my hair out!!

 

thank you so much in advance if you can help

 

 

I would highly recommend contacting a company called Absolut5. While they specialise in VW Transporters they will be most helpful with your issue.

not all of the harnesses are wired the same. My guess is the 12v supply is in an incorrect pin on one of the plugs. I had this on a previous T5. Much easier to get the correct harness rather than swapping wires.

good luck.

I had to supply a separate power feed to mine, I have an A3 (3 door 2004 - single DIN with BOSE speakers in the doors).

I spoke to dynamic Sounds who told me I needed the below kit.

Audi A3 (2002 - 2006) Full Bose Amplified Single Din Car CD Stereo Fascia Fitting Kit

FKIT-AUDI-16

 It didn't work out of the box, on speaking to them I had to supply a separate power feed to get it working. I may have some photo's if that helps ?. 

I just got an adpater from Halfords, get them to look at it and get the right one. Double din works perfect and switches off with car without losing memory etc