hi im new to this forum so i dont know if this is the right section for my quiery. anyway i have a 2005 audi a4(new shape, i think b7). anyway ive decided to change the stereo to a after-market one but im having difficulties. ive got all adapter which i need. ive got the ct51-au01, also the radio adapter aswel. fited everything and nothing works on the stereo, no power. ive done some research, and apparently i need to find a live, or switch live. could someone tell me what to do, on the ct51-au01, there is a blue cable which isnt fitted to anything, do i give the main power to this. if so how do i find the main live or is there something else i need to do.

 

Check out this link, I've not installed one on an A4, so I can't verify. If you got a wiring harness, it should have instructions as to what color is what.

Most head units have 2 power sources, a constant 12V source, typically a red or green wire, possibly fused and another power wire that is tied to the ignition switch. This one is often yellow or yellow/black.

The blue wire from your head unit is likely the remote turn on. You'd connect this to a external amp (or other relay) to switch it on only when the head unit is on.