How do I wire up these ditch lights?

Hi everybody. I bought some ditch lights. They have their own wiring harness with a built in fuse. At current I wired them up directly to the battery. SO much excess wire. I have a fuse tap and want to wire them up to something on the ignition in the under hood fuse box. What are people tapping into? What are you using for ground? I want to get ground also by the fuse box to limit the number of wires crossing the engine bay.

 

Use an add a fuse tap to this. There are grounds next to the fuse panel youre tapping into, unscrew one of the 10mm and add your ground wire to it.

 

@Rockpig. This is fantastic. Thank you for taking the time to take a picture. I wouldn't have thought the unused spots actually had power to them. I'll try. Found some grounds like you said. How did you get into the box? Little V cut out in the lid? It's sealed right up.