Light bar install, using roof pre-wiring

[4avor8ntfair]

Hey guys! I’ve seen a few light bar install how-to’s posted recently, but I couldn’t find any that show how to utilize the roof pre-wiring…other than one where they drill a hole in the roof…which I’m not going to do! I had seen a post on FB by Juggernaut Performance back in July and thought someone else might find this helpful. No, I’m not affiliated with JP, and Yes, I did get their permission to post this.

Also, I’m only posting the portion that’s different from others I’ve seen here, not the complete install.
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There are pre run accessory harnesses up to the right roof area, a pillar, and front and rear bumpers! We tapped the roof wiring for the light bar install. You can see in the pictures that there are small channels in the weatherstrip that seem to be made for this purpose. We passed our harness through, and then sealed it up with silicone. However, the drain channel is there, so the silicone was likely not necessary. We then wrapped right around into the trim panels. Both the outer panel and trim panel pop right off. Ford even provides new clips for this! As they don't always survive.

The visor is held on by one bolt, and a harness quick disconnect, then folds down and out of the hole. At this point you can see the upfitter wire there, taped to the main harness. Simple connect power to this wire, using the provided heat shrink and connector. Ford heat shrink is extremely nice, just make sure you heat it to the point of glue coming out both ends! We decided to ground with an eyelet and additional nut, on the weatherstrip stud, and it worked great.

Moving down to the right kick panel, we need to connect the roof lead to the main body lead. You can find both here, with two choices to jump over to the main fuse box area. We connected the roof harness wire to the white main wire.

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[Theherofails]

This is where I get confused on this process - are the pre-installed wires for signaling purposes or do they actually carry the current needed for the light bars? They seem fairly thin for high current requirements. I also have zero clue what the requirements are for LED lightbars to be honest.

 

[JediMcMuffin]

This is where I get confused on this process - are the pre-installed wires for signaling purposes or do they actually carry the current needed for the light bars? They seem fairly thin for high current requirements. I also have zero clue what the requirements are for LED lightbars to be honest.

The switches are signaling only, the pre-run wires are current carrying from the distribution point.

 

[Tadertodd]

This is where I get confused on this process - are the pre-installed wires for signaling purposes or do they actually carry the current needed for the light bars? They seem fairly thin for high current requirements. I also have zero clue what the requirements are for LED lightbars to be honest.

Most LED light bars take much less power than the big KC light style lights

 

[JPG]

Most LED light bars take much less power than the big KC light style lights

They do, but they still pull more power then this little wire can offer, IMHO There is a difference between a signal wire that will be asked to bring power intermittently and a light bar that will be constant when turned on. But i am no Electrician.

 

[4x4TruckLEDs.com]

They do, but they still pull more power then this little wire can offer, IMHO There is a difference between a signal wire that will be asked to bring power intermittently and a light bar that will be constant when turned on. But i am no Electrician.

Yeah I never understood why Ford used such small wires. I mean, they are not going far for power, thus the small wire, but they need to realize that not everybody understands power requirements.You're going to get guys trying to light up 30Amp bars with that tiny wire and it's gonna end up melting.

The roof wire is neat, but it's not as GOOD as we were all hoping. You either have to drill in and then seal around it (I mean hey, kudos for at least TRYING to think of us Ford) or run a wire under your weather seal. Or just down the window, which is what I'll be doing.

I give them a B- for the attempt. They lose points for not using a thicker wire and for making it a bit trickier to get to.

 

[cowman]

They do, but they still pull more power then this little wire can offer, IMHO There is a difference between a signal wire that will be asked to bring power intermittently and a light bar that will be constant when turned on. But i am no Electrician.

Wrong... I use the up lifter switches for light bars on both Ford and Dodge trucks... just look and see what switch is fused for the amp you need.... If memory serves they are different... from 10 amps to 30 amps...

 

[Dom]

Not sure wht the gauge is but here's a chart.....

What gauge are these wires?

https://www.powerstream.com/Wire_Size.htm

 

[redflipppper`]

Yes people need to know what they are doing here. The NEC shows how much amperage conductors can handle at ambient temperature and with continuous load. Also have to take into account overcurrent protection. Too much amperage across a wire that is not big enough will act as a choke and melt the wire, damage the components(s) or start a fire. If your not sure check the OEM requirements and stay with what they ask for.

 

[rdass623]

Yeah I never understood why Ford used such small wires. I mean, they are not going far for power, thus the small wire, but they need to realize that not everybody understands power requirements.You're going to get guys trying to light up 30Amp bars with that tiny wire and it's gonna end up melting.

The roof wire is neat, but it's not as GOOD as we were all hoping. You either have to drill in and then seal around it (I mean hey, kudos for at least TRYING to think of us Ford) or run a wire under your weather seal. Or just down the window, which is what I'll be doing.

I give them a B- for the attempt. They lose points for not using a thicker wire and for making it a bit trickier to get to.

does ford really need to contend with the foolish actions of owners making bad choices with modifications? these are nothing more than signal wires to actuate a relay. if someone burns one trying to jump start another car it is on them. part of growing up is making bad decisions and learning from them. back in the day, there were some who put a holley 750 on a stock 305 in a camaro and thought it would be faster... they learned quickly it did not idle...

 

[BadBoyBroncoBilly]

What is that wire GA 18 or 20? Depending on the amp draw of those lightbars you shouldn't have any problem powering them. It's not a continuous load so the wire ga should be just fine. I wouldn't get crazy with your roof top lighting. I wouldn't recommend running any more then 1 high quality low amp led lightbar with this wire ga.

 

[Hopeless Diamond]

I would definitely consider it a continuous load. Assuming your putting lights on to actually use them, not just as a fashion accessory. Going with the Baja Designs linkable or KC Hilites (amongst others) individual light bars you can get up over 16-20 amps. 16ga or smaller ain't going to cut it.

Nice of them to try, wonder if you could use it to pull a decent sized wire(s) through the A Piller. Doubt as they will probably have secured it every 6 mm.

 

[@BadBlueBronco]

regardless of gauge size the wires can be used to rerun larger gauge. It could be string for all I care.

 

[JediMcMuffin]

I would definitely consider it a continuous load. Assuming your putting lights on to actually use them, not just as a fashion accessory. Going with the Baja Designs linkable or KC Hilites (amongst others) individual light bars you can get up over 16-20 amps. 16ga or smaller ain't going to cut it.

Nice of them to try, wonder if you could use it to pull a decent sized wire(s) through the A Piller. Doubt as they will probably have secured it every 6 mm.

I had no idea those light bars drew that much power, I'm blown away. I'm gonna stop by Baja as they are just around the corner from me and ask them about the wiring.

 

[JediMcMuffin]

To me this table from Bronco Nation indicates the wiring to the accessory points is not 18GA, but closer to 14GA. Is this out of date or incorrect?

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