I just got a 9004 today to put in this homemade spotlight deal, I found this looking for the wiring for it. I see your post is a few months old so you probably already figured it out, but if not, here it is anyways. After looking around I found a picture of a wiring harness for the 9004 with a black wire and two reds, so here's he polarities: when your looking into the bottom of the headlight, have the flat part facing down, the tab on the left is the negative. The other two are positive, but I'm not sure which one is which as far as running n' stuff. You'll have to figure that out when you wire it, I'm gonna try runnin both tabs from one wire so I don't really have to worry about that. Good luck.