i searched for this and i couldnt find anything on head unit wiring like what i had but i got a 1987 mj they dont make a wiring harness for my truck but i have 2 black wires 1 is a ground i have a orange wire that goes to ground a purple one that is hot when i turn the key on and a green one that goes to my 2 speakers that i have in the doors does anyone know were the other black wire goes or does and why do i have 2 wires that go to ground?