Help needed Near disaster and I’m embarrassed to admit it

But I damn near burned my truck up today. Still not 100% sure what went wrong but I think it’s got to do with no relay while installing my kc hilite lzr 4” spent two hours running wire and trimming firewall of cab to get wire and switch conenetcd in truck. I’m still scratching my head. I freaked out when I turned the truck on and within a minute there was smoke coming from the switch from inside the cab... idk if I chafed a wire running in the hood or pulling thru the tiny hole to run it into the cab but man I got a damn good scare from it. New harnesses now about to be ordered if I decide to give it another try. Any help on what caused this to happen greatly appreciated. I kinda got into a hurry toward the end bc my kids had to be picked up from school so I keep thinking back and other than relay and circuit breaker which I do have I can’t really figure it out. No fuses blown everything running normally since but wires were freaking hot and nearly melted by time I got off the battery terminals. FYI I attempted to run directly to my new agm battery. I’ve read and read how to do this for a week straight and I feel like such a dumbass right now y’all! This could’ve been BAD

 

You might think about adding a fuse to the circuit if you didn't the first time around.

 

Actually had one added but maybe it wasn’t big enough. Only a 15 fuse... or maybe you’re meaning something different. The harness I used had an in line fuse.. u mean add a circuit fuse or what I had? Thanks for tip

 

You don't want a bigger fuse. You want a fuse properly rated for your application.

 

Thanks

 

Best thing to do is draw a picture of the whole circuit and every component. That way you can see what connects to what at a glance, and you can post it here so we can help you with it.

 

I’ll give it a shot

 

Agreed. 15 sounds like it may have been a bit big. A fuse needs to be just the right size, so it can actually blow when it needs too. I had the same problem a few years ago. Started an actual fire in the engine bay. I was using a fuse that was too big. I started smaller and kept going bigger until the fuse stopped blowing. I think I just run a 5 for my front light bar and another 5 for ditch lights. A relay likely wouldn’t hurt either. I always suggest using the provided harness(assuming a good brand of light is purchased, it will come with a good quality harness).

As the post above stated though, draw a diagram up and post it up. We will help you.

 

Working on the diagram now. I actually bought the leds from a fellow Tacoma world member used. I just used the harness that he sent along with the kc hilites. The harness came with an in line fuse w 15 in it

 

Let me see if I understand this. All the power to the lights goes thru the switch? See diagram for simple relay circuit. I would add a 30 amp fuse between battery and terminal 87B and maybe a 10 amp fuse between battery and switch. I would also use a small fused buss bar.

 

Most likely the wire was thick enough to handle n melt the covering before the fuse performed. Gotta be careful with routing through sharp edges...

 

This!! The exact type of harness that I used today

 

did the lights come on w hen you flipped the switch? Or did it just start smoking? Sounds to me like you've got a dead short against something thats grounded if its letting the smoke out of the switch.

 

I flipped it on Walked around truck to see the lights didn’t come on and by time I got back around I saw smoke coming from switch inside the cab

 

May have taken me 30 seconds to do the walk around and back. The thing is I know they were wired to the lights correctly bc before routing and trying installation I tested them while off the truck and they worked great

 

Yeah thats a short. Double check your wiring and your routing, make sure the insulation is intact. The firewall is a prime place for it to get cut up.

 

I mean I did have to get sort of rough pulling it thru to the cab and I had them stretched out pretty maxed to the lights themselves

 

You have a pic of where you routed the wires to the cab?

 

So should I buy a different harness ya think other than the one provided with a relay this time and should i go ahead and install circuit breaker as well? I’ve got all the stuff I just read a lot and decided that for this particular application I could get away with it for ditch lights wo. I’ve got an led bar too and just waiting for the brackets to arrive before installing. I just got off early today and got the itch to install my KCs I’ve been sitting on for a couple weeks now