Easy Roof Light Bar Wiring DIY

[Charlotte Kev]

Last weekend I tackled the last pice to my Bronco build…Heretic Studio 40” light bar for Trailrax.

During install research I saw where people were going thru the main wire fore wall grommet either on the drivers side or on the passenger side (most on the passenger side). As I went to install I started laying out the wire harness from battery up to firewall across to passenger side and looked for an alternate than going thru the passenger side grommet (kinda hard to reach and didn’t like the idea of cutting into it). Below is an alternative solution that I think is simple…maybe works for others.

In first photo you can see how the wiring from the battery to the passenger side is laid out. Straight up from battery and across the firewall to passenger side.

In second photo is where the deviation is. I ran the wire harness thru a gap under the mirror by the passenger fender panel.

You will want to remove the passenger door for east access for next step.

In the third photo you will want to remove the top two plastic panel clips in the door panel trim piece. This will allow you space to pull the wire harness thru. You will need to remove the waterproof connection points to get the wire to fit (this is same step in all other light bar wiring instructions/videos)

Once you pull the wire harness thru pull out the door panel weather stripping (you can leave it hanging as it’s temporary) as seen in the fourth and fifth photo. Stuff the wire harness in the cavity of the door frame (there is plenty of space)

After you run the wire harness up to the top of the door frame and thru an available slot you can reconnect the waterproof connector (see sixth photo)

Next step is to connect harness to wires from light. There are plenty of videos showing detail steps here as well so I will just quickly summarize.

In the seventh photo you will see where I poked small holes thru the soft rubber stripping for the roof panel seals. You will want to disconnect the wires from the wire bar and tape them up and run that side of the wires thru the rubber stripping holes. Leave the waterproof connector where you want to have for connection to the wire harness. I left mine in the cavity above the door frame which you can see in the sixth photo. There are other options.

From there reconnect positive and negative wires to light bar and tuck everything back up.

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[GroovyGeek]

If you have the aux switches you can drill a hole near the mounting bracket and hook into the existing wiring.

 

[Charlotte Kev]

I have aux switches…and that’s really not a great idea for that size of bar. The prewired wire gauge is way too small. Also no need to drill. Wired up to aux 1 with wire harness. Then ran power and ground directly to battery. All aux switch’s are full now.

 

[Tex]

This is more or less how I wired mine up as well. It's a shame the existing aux wiring is so small...I'm not even sure what you'd use it for honestly.

 

[HoosierSquatch]

Thanks for posting this. I’m just waiting on my rack and will be doing this soon.

 

[Charlotte Kev]

Thanks for posting this. I’m just waiting on my rack and will be doing this soon.

🫡

 

[Charlotte Kev]

This is more or less how I wired mine up as well. It's a shame the existing aux wiring is so small...I'm not even sure what you'd use it for honestly.

I want to give them A for effort here…but can’t. Really weird how they thought all of this out just to put a tiny wire gauge.

 

[TrailBuddah]

Thanks for posting this! I wasn’t crazy about cutting through one of the firewall grommets either. So, this looks like a good alternative. Much appreciated! It is a shame about the pre-run factory wires. Maybe they’ll use more robust wiring in future model years. Take note, Ford!

 

[Charlotte Kev]

NP. Maybe it works good for others as well.🫡

 

[Lej512]

I want to give them A for effort here…but can’t. Really weird how they thought all of this out just to put a tiny wire gauge.

If you, or someone you know is savvy in the field of 12 volt wiring, relays are the way to go. You can connect a high amperage device through a relay and still use the small gauge factory circuits to control it.

 

[Charlotte Kev]

If you, or someone you know is savvy in the field of 12 volt wiring, relays are the way to go. You can connect a high amperage device through a relay and still use the small gauge factory circuits to control it.

Sure…but why? You would still have to drill into and run wire through. I guess you could and maybe save like $30? Wires harness was ~$50. Anyways…multiple options to do.

 

[A51Bronco]

It is a nice walkthrough for those without aux switches or those that want to not use the factory wiring. I'm rocking factory wiring because it is simple and does the job for me.

 

[cr117]

It is a nice walkthrough for those without aux switches or those that want to not use the factory wiring. I'm rocking factory wiring because it is simple and does the job for me.

All broncos have the factory wiring regardless if they have the aux switches or not. However, the factory pre-run wires are something like 16 gauge, not nearly enough for the close to 30 amps needed for a light bar of this size. If you’re connecting a 40” light bar with a 16 gauge wire, you’re putting your bronco at risk of burning to the ground.

 

[Charlotte Kev]

It is a nice walkthrough for those without aux switches or those that want to not use the factory wiring. I'm rocking factory wiring because it is simple and does the job for me.

I am using factory Aux switches for all my lights. Have the full panel in use actually. In all cases except two I have run power direct to battery and used wire harness toggle switch wire to connect to aux pre-wire. The two that I connected direct to pre-wire aux where small amp draws so no risk there.

 

[denneyt]

All broncos have the factory wiring regardless if they have the aux switches or not. However, the factory pre-run wires are something like 16 gauge, not nearly enough for the close to 30 amps needed for a light bar of this size. If you’re connecting a 40” light bar with a 16 gauge wire, you’re putting your bronco at risk of burning to the ground.

Switch 1 is rated at 30 amps and engineers aren't dumb the wiring got changed for that 30 amp fuse, and wiring can flow surprisingly high current through a surprisingly small wire.

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