How do I build a wiring harness?

Next project is to wire up LED lights in my bed. I want them to come on or off anytime the truck's cargo light is activated (thus, door open, switched ON, etc.)

Yes, I'm aware there are kits like Matt Gecko's that would make my life easier.

But then I wouldn't learn how to do this for the next time, or future projects.

I'm going to use these VLEDs for this. But they don't come with a harness or easy plug and play connectors.

I'm not sure if I can use Duotaps somehow or if I have to create a full harness of some kind--much less how one would do that.

Please note I am not an electrician. I don't mind learning, I don't mind taking time to do this right, and I don't mind the risk. I've done some electrical wiring before, but it was relatively straight forward -- soldering a phone charger into a cig socket for constant 12volt power, for example.

Just need some guidance on how I would do this. The closer to step-by-steps the better, but I'll take anything that orients me in the right direction to start.

 

Looks like low draw but for an outlet (in this case lights)
You need a switch
You need a power source
You need a ground.

The switch is whatever fuse/wire gets energized when you open your door.
I would not use this as a power source - It wasn't designed for that.
So now you need a relay. Your door power plus the relay = your switch
Power is your battery
Ground is your battery or a good contact with the frame or body.

A harness is wires of adequate size for your voltage and run length, that looks pretty.

 

https://www.tundras.com/threads/led-lights.79447/

I was involved in this thread a while back. Not really about wiring bed lights but the process would be the same your destination is just different. A t-tap would work for the way I wired mine up in my explanation but it is a little difficult to get a good connection with a tap on such small gauge wiring.

 

Seems like we went over some of this already.

https://www.tundras.com/threads/anyone-using-vled’s-striplight-bars.103284/

 

But you don’t have to use tiny wires. My first wiring project was chase/dust lights. I used 12awg, and did home runs for each of the two lights, all the way to my switch panel…, where I connected them to the same terminal, of course , so the switch would activate both. Because I was new at it, didn’t really understand it, so I was afraid to daisy chain the two lights and run only one set the length of the truck. My point being, the best way to learn is by doing.

So your harness can be as easy as two wires that connect to the light*. For ease in learning, use a red shielded wire for + and a black shielded wire for -. The other end of the red goes to one side of your switch; then run another length of red out to your battery. Think of this as one run of red shielded wire with a switch included. That switch basically toggles, connecting/ disconnecting the light to the power. Meanwhile, run the black between the light and the negative post of your battery, as your ground. As has been said, you could ground to a clean area of chassis instead of running all the way to the battery but, IMO, overbuilding your first project, keeping everything direct and easy to understand, will help you learn, and be an easy reminder next time.

* CAUTION: this is meant as a simple overview about “how to make a harness”. I must add that the harness I purchased for my light bar includes an in-line fuse. You’ll have to rely on “brighter” brains than mine to help you figure out amp draw and what-not, to know if you’ll need a fuse, etc.

 

After re-reading your post, I’d tell you you’ll tap into the door as your power source, as already suggested (not all the way to the battery). So probably, red wire from light——> switch——> door wire. Black from light ——> chassis.

I left what I wrote because it’s a very simple overview of the big picture. I noticed someone linked to a post where maybe your question was asked and answered. I remember being new on this forum and knowing not enough to make sense of so much info. So that’s why I wrote an oversimplified description. I hope it helps.

 

Others covered the basics. Just a tip, I would not make the bed light dependant on door open or cargo light. You might need to use the bed lights loading, unloading and you don't want to have to open the cab door or switch the top cargo light on extra for that. If you run 2 wires to the battery ( positive and ground ) with an inline switch at the tailgate then add an inline fuse (10A is sufficient ) and you don't need to wire into the cab at all. Just run your wires at the frame along factory harness to the engine compartment and battery.

 

sorta. But not really. I posted that thread mostly to help narrow my LED options. I’m pretty much sold on the VLEDs now, but need to figure out how to wire it. The precious thread just touched on it; I’m trying to dive deeper into step by step specifics here.