Hey there, I've got a auxiliary light install that I'm trying to figure out and I've come here for some guidance.
The light kit came with a wire harness but it's far too short to reach where i need it to go, I think it's meant for bumper light installations. I need to run about 9 feet of power and ground, at the farthest point, from the lights to the relay. The power and grounds on the kit harness are 16 gauge. I figure I can just replace those power and grounds with new longer lengths of 12 gauge.

The lights have 100w bulbs in them. The issue I'm truly facing is that the headlight housings are pre-wired in 18 gauge for power to the bulb and ground to the metal housing. I was told at a local electrical parts store it'd be fine to snip the 18 gauge bullet connectors off the ends of the housing wires and splice in some 12 gauge wire and connectors. That just doesn't feel right to me... I want to wire these for safety and performance.

My question is, can I just re-wire the housing in 12 gauge? Take the 18 gauge out and replace it with 12 for power to the bulb and ground to the metal housing, throw on an appropriate connector and then run the rest in the longer 12 to the relay?

The kit included a 20 amp relay, fused battery power wire, fused signal wire and switch.

Here are a couple of pictures of the light housing wires.

Thank you much in advance. I'm eager to get this project underway and get these lights up!

 

You should be fine running larger gauge to light harness. But I don't like that open spade on the positive lead between reflector and housing. Looks like reflector is metal.

 

Thanks for the reply!

That positive spade is covered by a protective sleeve (white). You can see it in the first picture.

So... 12 gauge to the bulb wire (blue) and a 12 gauge ground to the metal housing where the small ground is now. Out the back of the light housing, connectors and I'm good to go?
Or you mean I'll be fine running 12 gauge to the 18 that exists?

 

Check out a wiring chart. You want bigger wire gauge for greater distance as you mentioned earlier. So if housing is water tight and run of thinner wire is short it shouldn't be a problem. After you install you can check wires for excessive heat. But might be easier to do it all at once and seal housing back up watertight. I wouldn't change wire from spade to bulb.

What are you going to encase wires in? How are you going to route them?

 

This^^^

I think 12AWG is good for 100W... But verify as Muddpig suggests.

 

Yeah Google is your friend here..

Voltage drop is based of the resistance of the wire, resistance is based on the quality. The wire supplier will have an average ohm/ft of the wire..

 

I was planning on splicing the two power wires for the lights together into a Y and then run just one wire to the relay. That one wire will have to be about 8 feet long from where the lights will connect. I checked this site, https://www.wirebarn.com/Wire-Calculator-_ep_41.html, and it says I'll need 8 gauge wire! Yikes... I'm still trying to figure a clever way to route the power and ground from the lights.


As far as covering the wiring, I was thinking of using fiberglass wire sleeve. Flexible and affordable. The lights say water resistant, yet I don't see how. There's no gasket between the lens housing and the plastic case. Maybe I can seal it up with silicone?

 

I've looked at different types of wire. I've decided to avoid the auto parts store stuff. I'm considering marine grade tinned wire right now but I'm still looking into that.

 

routing: battery to distribution block in the engine bay (heavy guage wire! You'll need to source this. In the engine bay is a good place it allows for adding a wench or other auxiliary circuits.), from distribution block thru firewall (needs a new hole and grommet), relay under the dash, power along A pillars and through the roof (another grommet, a good one maybe even a marine grade bulkhead passthru). Yes it is good playing with other people's money! ... The benefits of running heavy gauge all the way out to the rack allow you to put more flood lights, if you decide to do this at a later date, its all about the ability to upgrade with side or rear floodlight.

Current draw: you want to measure what the lamps are pulling before you make any decision. Wire them up, temporary, to the battery with the engine running and see what they are actually drawing. This will give you a better idea of what you actually need for wire size and expected voltage drops.

Voltage drop: if you can rig up an array of c-d cell batteries try them on those at a lower voltage (between eight 9.6v and ten cells 12.2, compare that against the battery voltage with engine running) to get an idea of how much you are willing to accept. That calculate app you linked defaulted to 2%, that is probably excessive something like 10% might be more managable , but it's going to give really good power.

Welcome to the world of electrical engineering. You can do the tests and math or just go overkill and spend the money.

 

Hows this for distribution? https://www.bluesea.com/products/502..._Bus_and_Cover

I've gotta avoid drilling through the roof. I was thinking under the drip molding would be suitable. Down along the windshield trim and into the bay.

Thank you for all of the info so far! It's coming together but it seems like it's gonna be more work than I thought. Learning process.

How would I wire the lights temporarily to test their actual draw?

 

I re wired the lights today. I replaced the 18 gauge in the housing with 12 gauge. I just need to attach plugs to the ends. I'll use 12 gauge throughout the rest of the harness. I think it turned out great!


I used fiberglass woven insulation sleeve to protect the wires, it's also rated for 270F. I'll use it throughout the rest of the harness too.

 

 

Will do. Thank you guys for the help so far!

Just gotta find weather proof plugs. I looked into the weather pack ones but they didn't have any in 12 gauge.

 

Looks clean! Details of how I'd seal...
Silicone around each wire before you slip the grommet over them,
Silicone around the grommet before you insert it in the plastic housing,
Silicone around the wires and grommet before you slip the insulation sleeve over them.
Silicone perimeter of the the housing before you put the plastic housing over it, then the bolts.

I like the trailer housing connectors like this... Simple, yet water resistant, polarity-keyed, and you can tape over it for extra measure. Not sure if it comes in 12AWG though.

 

Looks like I'll be helping to keep some silicone company in business haha.

I've got those trailer connectors sitting around right now, 12 gauge. I suppose I can use those. I like a good clip and snap sound with connectors though... but those will do.