Help with wiring diagram for 4 led's

Hello all-
So I'm going to run some led bars in the front and rear. Mostly just for putting the boat in and out of the water at dawn/dusk so I don't need a huge light bar. The front is going to have two 36w 8" bars, and the rear two 18w 7" bars. My plan is to buy this harness which has two leads and run one to the front and run one to the back. I would double off each lead since I think both lights are small enough wattage. I drew a little diagram. What do you guys think? Should I lower the fuses? The kit comes with 30a but I don't think I need that much. Thanks for your help.

 

Looks good if not a bit overkill. A pair of those lights is 72watt = 6amp at 12v here's a converter calculator. You can also run all 4 on one relay, if judging by your diagram that you want them all on with the same switch. Good practice to have the switch powered by the ignition power so they turn off when the trucks not on.

 

One issue you might run into is length of wiring with that harness. I typically think those pre-made harnesses are cheesey and too much to fiddle with, I like to wire my stuff more factory and have the switch hooked up to dash light circuit, but I have all the tools to build my own.

 

That's what I thought, but extending the power to the led's isn't that hard. I've just never wired a relay. After I did the amp calcs I'm thinking I might even step up to a 32" light bar in the front and the 36w lights in the back and I'm still only at 22 amps and can run this harness. I would probably just go down to one relay.

 

You just gotta watch out what size wire your harness uses, and how long you extend the wires. Voltage drops(decreases) based on the resistance of the gauge and length of wire. A 10% voltage drop is sufficient for non-critical accessories like lights, though some people like 3% or less.. Always step up to the next step, I.E. You got 72watt =6amp to one pair, use 10amp in the chart.



Hooking up relays is pretty simple, granted I always have to verify by looking at a diagram.

 

Thanks so much. I was looking at harnesses with 14awg cable and 12' leads...I would rather buy a harness i know i'm not screwing up wiring on than chance my battery and warranty. haven't even had the first oil change.

 

I would run 14ga wire to the front and rear, and 'Y' them together at the relay spade connector.

 

Perfect, you got this!

 

If/when you get more accessories and more wire clutter on your battery there are some good management solutions. Bussmann rtmr boxes that I build and sell, Blueseas, SPOD, and plenty of others. They clean things up nicely and look pretty professional!

 

Expect to need more than 12 feet of wire to run all the way back. Start with 20', this will give you wiggle room while running the wire along the frame and such. Stick with waterproof connectors when connecting the harness to the lights. Corrosion will bite you in the ass at some point if you don't. Dielectric grease is cheap insurance and will help combat corriosion in the connector plugs. Use a waterproof relay for under the hood also.

One other thing to note with those harnesses, it looks like the switch power is fed from the relay. If you choose a switched 12 volt source to run to the switch, you will need to take care of the left over "hot" wire.

 

Great advice @fergyz thanks so much. When you say take care of the left over hot wire do you mean just cap and tape it?

 

I just checked the diagram for the link he posted, and just generally knowing these setups but no power is fed from the relay to the switch. The switch feeds power to the coil side of the relay. A lot of times the same battery power lead is jumpered to the switch and relay, meaning the harness will be hot all the time.

 

Here is the Diagram with some notes added.

 

I guess I should have worded it differently... but I agree with the input power for the switch is generally ran from the fused battery wire at the relay making it "hot" all the time. Both wires are crimped into the same terminal connector. This is what i meant in the first place.

Rigid, Piaa and various other harnesses are typically done this way.

 

I usually clip the connector off and slide a piece of heat shrink over the end of the wire. I leave part of the heat shrink extended past the end of the wire. once heated it will shrink down but not all the way. while its still hot i will quickly pinch and release the end and that will close the end of the tubing. KEYWORD - quickly...

 

For those lamps the boat switch you are showing will handle the amps without a relay. If it's an On-Off-On (dpdt) then you could also handle the lamps as rear only or both on.

 

Why are you putting them both on 1 switch? I would have 2 separate circuits. If you are using the lights in front to see where your driving you dont want to blind people behind you. If you are using the ones on the back as back up lights as you back into the water, no need to blind other people up higher on the boat ramp waiting there turn.

 

Maybe while the truck is getting to the ramp, leaving the ramp or even preparing the boat at dawn, dusk or night he could use all light available...

 

These lights are just for prepping the boat and unloading gear in the morning to go hunting. Got my harness. Do you think I can put both the positive and negatives on one ring terminal connector and connect to the battery?