went to the junkyard today to find an electric fan, i found a newer, like late 99 or early to mid 2000 import with some really slim dual 10" system and figured those would work great, so here i got them home and pulled took off the plug in for the factory system, there were only 2 wires i figured easy, power and ground, black would be the ground, then there was a blue wire and now im confused as to weather that is poer or something else, wt can u guys add?