How do I move or add another third brake light when adding a DIY canopy?

[zolland]

I'm building a camper that sits on the bed like a canopy and will extend over the cab and therefore block the third brake light. Is there a best practice or known product for adding a third brake light to the back of my camper?

Do people usually just hook into the wiring harness for the trailer hitch? Or would it make more sense to take out the OEM third light and plug in there? Ideally I'd like to keep the OEM third light installed so if I ever take the trailer off to do something I won't have to worry about making it.

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[Glen Baker LLC]

Is there a reason why you could not keep it on the back of your cab? Buying a separate third brake light put on the back of your canopy. If you used a third brake light off of ANY truck in the junkyard. You could then tie in the wires from your third brake light. That way you would also have the white bed lights in the back to shine when you needed them.
Just tossing out ideas.

 

[Waterick]

I don't believe you can use the trailer wiring for anything but a trailer (something about it sensing a hook up). Best to get another fixture and power it from exiting CHSL circuit/wiring.
Edit: there are people here who have done this, you will get a better answer.

 

[zolland]

Is there a reason why you could not keep it on the back of your cab? Buying a separate third brake light put on the back of your canopy.

Nothing stopping me, that's what I was thinking would be the cleanest solution as well... although tying into the existing wires worries me a bit. Not sure what they have going on in there, if it has the power to run another set of lights, if the added resistance will throw some warning, idk.

existing CHSL circuit/wiring

This is the wiring coming out of the bed of the truck?

 

[Sticks]

Nothing stopping me, that's what I was thinking would be the cleanest solution as well... although tying into the existing wires worries me a bit. Not sure what they have going on in there, if it has the power to run another set of lights, if the added resistance will throw some warning, idk.

The BCM is pretty sensitive on these trucks. If it senses the lamp's current draw is too high, it will shut the light off. You'll probably need to run a relay that is triggered by the original light, rather than powering another light directly from it.

Waterick is correct-- you cannot power a light off the trailer plug. It will think you hooked up a trailer and throw a bunch of errors.

I think Putco might make a tailgate brake light bar that uses auxiliary power and senses the brake signal at the tail lights-- if so, this could be a cool option.

 

[zolland]

That Putco is a good option but is pretty expensive at $354, also not a huge fan of it in general... wanted something a bit smaller, that thing would extend across the entire top of my canopy.

You'll probably need to run a relay that is triggered by the original light, rather than powering another light directly from it.

This is a good idea, but I am unfamiliar with relays. Is this the system you are proposing? I get an aftermarket LED third brake light, and a relay for the brake light. Pin 30 goes to power (potentially the 12V connector in the bed of the truck), 87 to the light, 86 is intercepted from the actual light, and 85 is ground. Running light just hooks right up to 12v.

This would allow them to both work at the same time right? That would be pretty sweet.

Do you know where I could get a splitter for the third brake light harness so I don't have to splice any wires? Worried that will void warranty or something... would also be a bit more elegant

 

[Sticks]

This is a good idea, but I am unfamiliar with relays. Is this the system you are proposing? I get an aftermarket LED third brake light, and a relay for the brake light. Pin 30 goes to power (potentially the 12V connector in the bed of the truck), 87 to the light, 86 is intercepted from the actual light, and 85 is ground. Running light just hooks right up to 12v.

This would allow them to both work at the same time right? That would be pretty sweet.

Yes, that is exactly how you would wire up the relay. The 12V connector in the bed is a great 12V source. Third brake lights don't have a running light, it's just brake and a white bed light.

Do you know where I could get a splitter for the third brake light harness so I don't have to splice any wires? Worried that will void warranty or something... would also be a bit more elegant

You'll probably need to make a splitter yourself. You could get a replacement pigtail for the vehicle side of the harness, and cut up a replacement third brake light harness for the other side. The pigtail for the vehicle-side of the third brake is Ford Part# WPT-1103 (Yikes, it's around $40). Looks like you can get a used third brake side harness for like $14 on Ebay (https://www.ebay.com/itm/315631634159).

The Maverick uses the exact same third brake light as the 2015-2020 F150. Any 15-20 F150 housing or harness should work as long as it doesn't have a cutout for a rear-facing camera in the housing. Those are old enough that you might be able to find one in a junk yard to take the harnesses out of.

 

[MetalsGeek]

The trailer connector is inappropriate for a 3rd brake light because of the way the turn signals work as well as the logic that detects an attached trailer. e.g. Even if you use diodes on each of the brake/turn signals, your extra stop lamp will blink with either one. The cleanest approach is to put a Tee splice into the high-mount stop line behind the back seat on the passenger's side and run that to your new low-current LED hi-mount stop lamp.

 

[MakinDoForNow]

The trailer connector is inappropriate for a 3rd brake light because of the way the turn signals work as well as the logic that detects an attached trailer. e.g. Even if you use diodes on each of the brake/turn signals, your extra stop lamp will blink with either one. The cleanest approach is to put a Tee splice into the high-mount stop line behind the back seat on the passenger's side and run that to your new low-current LED hi-mount stop lamp.

Check curt they have a relay setup for trailers which uses it own power from battery positive. Does not come with light bar but is affordable but easy to install.

 

[zolland]

Awesome this is all super helpful

You could get a replacement pigtail for the vehicle side of the harness, and cut up a replacement third brake light harness for the other side. The pigtail for the vehicle-side of the third brake is Ford Part# WPT-1103 (Yikes, it's around $40). Looks like you can get a used third brake side harness for like $14 on Ebay (https://www.ebay.com/itm/315631634159).

This sounds like a good avenue to explore. I'd love to add an extension in the middle that intercepts the signal rather than cutting into my harness, but if the third brake light side harness is so cheap maybe I'll just keep my OEM and cut up a spare... they don't seem super easy to replace though.

By the way, any tips on running a wire from the cab near the third brake light out to the bed of the truck? Or above the bed?

Even if you use diodes on each of the brake/turn signals, your extra stop lamp will blink with either one.

Ahh, I see the issue now lol

Check curt

Looks like theirs go for around $100 which is pretty steep... and seems like they are hooking into the

 

[tom_tucker]

I have an ARE MX and I'm sure (the third brake light) is connected with a plug-and-play splitter harness installed on the rear driver's side tail light. I've also used that tail light for a 4 pin connector on another car. I'm sure etrailer has something.

 

[zolland]

I have an ARE MX and I'm sure (the third brake light) is connected with a plug-and-play splitter harness installed on the rear driver's side tail light. I've also used that tail light for a 4 pin connector on another car. I'm sure etrailer has something.

Actually yeah idk why I've been so hung up on intercepting the third brake light wires, accessing the wiring for the tail light would be a lot closer to the new third brake light of my canopy... How do the wires exit the housing of the tail light?

 

[tom_tucker]

Actually yeah idk why I've been so hung up on intercepting the third brake light wires, accessing the wiring for the tail light would be a lot closer to the new third brake light of my canopy... How do the wires exit the housing of the tail light?

I'm sure the harness is external to the tail light housing, but I get what you're asking. Comes through the top hole just below the bed rail from back to front.

 

[MakinDoForNow]

Actually yeah idk why I've been so hung up on intercepting the third brake light wires, accessing the wiring for the tail light would be a lot closer to the new third brake light of my canopy... How do the wires exit the housing of the tail light?

The wires for the curt T adaptor plugs between the trucks tail light harness end and the tail light housing on both drivers and passenger side and can be routed to the hitch area or where ever you want under or in the bed. There is also a power wire that needs to run from battery positive which has a fuse (depending on wire size can be 20-30 amp you could use the 20 amp drop for bed on passenger side but I believe it's fused with rear seat power point.) placed near battery post positive. With this installed in addition to the factory four pin trailer plug if it's installed you would have two four pin plugs one for use with a trailer using the trucks towing a trailer program and one for possibly towing without the truck thinking there is a trailer if you think that's wise! But you would have full brake light functions without turning off truck functions, etc. E-trailer can supply the curt device or they have a different brand also.

 

[zolland]

I'm sure the harness is external to the tail light housing

Yep sorry, meant how does it go from the housing to the bed. I see now, pretty sweet those holes and grommets are there.

curt T adaptor

Just to be clear, you are talking about one of these right? For posterity, I am linking to a Curt product titled Custom Wiring Harness, 4-Way Flat Output, Select Ford F-150 #56465. I hate scrolling through an old post with cryptic dead links...

https://www.curtmfg.com/part/56465

That just seems like a lot of unnecessary complexity and cost. The rest of the infra for a trailer would be lost on this project that only needs one light.

Looks like I can get a FoMoCo 12V relay for like $10 on ebay, a 20 amp fuse for like $10, and an aftermarket rear third brake light for around $10. I then just want to find a way to make an extension for the tail light cable so I can intercept it the same way the Curt product does. If I could then 3D print a housing that would be a sweet setup!

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