No head lights or horn

[Devin]

So I went and did a little off roading and when I got back home I realized I had no more headlights or horn. Both fuses are intact and nothing seems knocked out of place. This is a good opportunity to get better at my electrical game. Where would someone who knows electrical start?

[teranfirbt]

I would start by checking to see if you have power at each thing with a multimeter. With the headlights on low beam, the top pin in the connector should have 12v. If it does, then you might have a ground problem. If it doesn't, see if you have 12v at the headlight relays and then fuse. I've seen old fuses break from vibration and lose connection, but look normal. If you were wheeling you might have hit a bump and cracked a fuse.
summary is, see if you have a power or ground problem.

[Devin]

Thanks for the reply. That's good advice to determine whether its a ground or power issue. Mine was a power issue, and upon closer inspection I found a wire had come out of that little black box with two wires that goes from the battery to the alternator. What is that thing anyway?