Installing a sony CDX-GT 510 into my 87 audi quattro 5000cs turbo. I'm getting sound from my rear speakers, but its very low because i cant get my amp to turn on. I cant find the wire from the stock wiring to connect to the amp turn on. It should be a white wire but there isn't one there. In the trunk coming out of my amp is a white wire and I tried connecting speaker wire from that and running it directly to the stereo but it still did not work. I dont know if i made the wrong connection or what. Im baffled and have no clue what to do or check for.....any help?