NE-truck
you can use a volt meter if you have one by finding the constant the ground and the 12v switch then speaker pop using a 9v batter by touching each one of the the speaker wires to the battery one at a time example(because that doesn't make Sense)touch the blue wire to the poss of the 9v and hold it on there while touching the the other wires (one at a time) to the neg side of the 9v battery when one of the speakers pop mark down which speaker and color of the wires. another thing use the dark color of each speaker as the neg to your cd player