Originally Posted by Warlock III
They may have never messed with the factory amp/wiring. The (Blue?) antenna/trigger wire probably wasn't connected because of that.
I have a few blue wires and they are all labeled, Power Ant, Power Ant, and Amp Turn on, Amp turn on isn't connect to anything, and to get power to the headunit once the harness is connected to the back you need to have the Antenna plugged in, if that gives you any clues.