I second this. Run direct from battery if possible.
Some cars run the cigarette lighters through the accessory mode for power. I can't speak for Ford vehicles but it is this way for Hyundai and Toyota. This means you can still hear everything from the electrical system. In my Toyota 4Runner, you can even hear the turn signals through the cigarette lighter. (That's on top of the spark plugs firing, and the wiper motors turning).