I have a 2007 escalade and I just bought 2 pairs of the 5th Gen projector ghost lights. I got the front doors installed and they work fine, I just spliced into the existing courtesy lights at the bottom of the door. The problem is the rear doors, they don't have a courtesy light. Can anybody tell me what wires I can spice into for this to work? I know it can be done because when the doors open the dome lights come on so there is some kind of switch. I was reading and people were saying there is a negative ground wire that completes a circuit when the door opens and that can be used for this.