I have an Audi A4 B7 Convertible which has a double din Concert 2 radio CD player. I haven't got a 6 CD changer so I want to add an auxiliary input lead. The unit is one with two 8 pin sockets on the back vertically positioned and below there are two twelve pin sockets.

The original 12 pin socket which would normally have the CD changer plugged into it just has one wire on pin 5 which is labelled as BOSE and nothing more. I bought a lead with a plug on to go into this 12 pin socket. I also bought a different lead which has a bluetooth receiver at the end. Oddly the two leads seem to have different views of which pins to connect to. The simple lead connects to pins 1 and 7 for input, labelled NF-IN left and right according to the wiring diagram I have, but the bluetooth one connects to pins 8 and 9 which are CD audio in.

Its all a bit academic really as neither work! So my question is what pins should be connected for auxiliary input, and how does my head unit recognise that it is there? It doesn't see any input when selecting CDC and I have no obvious other auxiliary input.