i have a 2004 f150 and i bought an led tailgate strip $60 bucks off ebay and it says to splice one of the wires into the positive/hot wire of the reverse light so i the reverse light on the tailgate strip works.. anybody know which is the hot? mine has a black and a black with purple line for wires leading to plug in on bulb... any help greatly appreciated.

 

the reverse light for the seven pin connector is the purple one but it only has power when the truck is in reverse

 

ok thanks a bunch i figured solid black was negative but wanted to double check