Switch, Upfitter, or Harness: How to Power a Truck Light Set
Every light set we sell, rock lights, wheel lights, valance strands, all of it, needs a source of power. The lights are the easy part. The question that trips people up is how to feed them cleanly and safely, with a fuse in the line and a switch you can reach. There are three good ways to do it. Here is how each one works and when it makes sense.
Every light set needs a power source
A light kit gives you the lights and the wire between them. It does not give you a spot in your fuse box. Somewhere between the battery and the lights you need two things, a fuse so a short cannot start a fire, and a switch so the lights are not on every time the truck is. The three options below are just three ways to provide those two things.
Option one, a switched and fused circuit
The classic way is to build the circuit yourself. You run power from the battery through an inline fuse, to a switch inside the cab, and out to the lights, with a clean ground back to bare metal. It is the most flexible option because you choose the switch, the fuse size, and the routing. It is also the most work, because you are making every connection and drilling for the switch. If you go this way, size the fuse to your set and use wire heavy enough to carry it. Our fifty foot spool of two pin sixteen gauge wire carries a full light set and leaves slack for tidy routing.
Option two, a factory upfitter switch
Many trucks come with upfitter switches, a small bank of auxiliary switches on the dash that the factory already wired to a protected power source. If your truck has them, they are a clean place to tie in, because the fuse and the switch are already there and the wiring is meant for exactly this. You run the light lead to the upfitter output, ground it, and you are done. Check your owner manual to see if your truck has upfitter switches and what each one is rated to carry before you load one up.
Option three, a harness that brings its own relay and fuse
The simplest path for most people is a harness that already has the hard parts built in. Our wiring harness and wireless remote carries a relay, a switch, and a fuse, with one lead that has both a positive and a negative connection. You bolt the leads to the battery, plug in the lights, and control them from the wireless remote. There is no separate switch to mount and no fuse holder to source, because the harness is the switched and fused circuit, already made.
Which size harness you need
The harness comes in two sizes, and the size is about how much current the set pulls. The thirty amp harness on fourteen gauge wire is the common choice for a rock light or wheel light install. The forty amp harness on ten gauge wire is there for a bigger draw. Match the harness to the set you are running, not the other way around, and you will not be guessing later.
Wire gauge and fuse basics
Two rules keep a light circuit safe. First, the wire has to be heavy enough for the current, which is why we spool a sixteen gauge two pin wire for light sets rather than something thinner. Second, the fuse has to be in the line and sized for the set, so that a pinched wire blows a fuse instead of cooking the harness. A harness handles both for you. A hand built circuit puts both choices in your hands, so make them on purpose.
What to have ready before you order
Before you buy, decide which of the three paths you want, because it changes what lands in your cart. If you want it simple, add the harness. If you are building it yourself, add the wire and pick your fuse and switch. If you have upfitter switches, you may need nothing but the lights and a short lead. To see the whole picture with a set on the vehicle, read our guide to valance lights and the notes on our rock light installation page.