Trailer Connector for Trailer With 4-Way To Add Reverse Lights

Question

Question:

Hi, We now have a 2014 Silverado 1500 Double cab work truck and it appears to be pre-wired for both 4 way flat plugs and round 7 pin plugs. Our current boat trailer harness is 4 way flat and does not have allowance on the trailer lights or harness for back up lights. I would like to have backup lights option because I will be adding a wirelessinch rear view camera for the truck and would need something different for wiring on the trailer to be able to accommodate an extra wire for back-up lights on the boat trailer, which also is preferable for adding a second rear camera on the boat trailer and while the transmission signal is wireless it still needs power preferably from backup lights to add the 2nd camera that would come on when you shift into reverse when boat trailer is connected. So largely to accomplish this given there are both the 4 way flat connectors and the 7 pin round male connector mounted to the bumper, I need to know what harness I need for the trailer to be able to wire for and operate back-up lights to power the the second camera to be added to the rear of the boat trailer. Hopefully what I would like to accomplish is clear enough. Not sure on total length of the trailer and boat boat but I believe it is considered to be wishbone style and the boat itself is approximately 16foot 5inch so that length of trailer and boat needs taken into account with regards to harness length. Your expertise in the above regards is appreciated in suggesting what harness and or cable connections are required given what is already wired on the truck and what isnt done regarding a harness for the trailer along with the proper cable to connect to the 7 pin female connector on the back of the truck. I will have to add different trailer lights on the back that have wires and bulbs for wiring for back-up/reverse lights. I have and tried uploading photos but it didnt complete process for some reason.

asked by: Dave

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Expert Reply:

Hey Dave, welcome back! Since you have a 7-way on your truck the best solution would be to add one to your trailer. What I would do is add the etrailer Trailer Wiring 7-Way Upgrade Kit w/ Junction Box and RV Style Connector # e99011. You will cut off the end of your existing 4-way and wire it into the junction box. Then you can take some additional wire like # 10-1-1 and run that back for your reverse light circuit.

expert reply by: Robin H

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Junction Box
(click to enlarge)

Dave

6/24/2026

That sounds simple enough to accomplish what I need ! As it is I do not have trailer brakes so it appears I mainly would need to add the blue wiring as suggested for the reverse lights. I also assume I would need to run two wires, one for each rear trailer light and or run one wire back to the light on the passenger side and piggyback to the correct wire for reverse on the other side. Unfortunately, while my existing LED trailer lights do not have a reverse light function I would need to locate a set of waterproof trailer lights that feature a reverse and license plate light on one side and side marker and reverse on the other side. Either that or leave existing lights on without the reverse light function but run the blue wire representing reverse light back to the area the reverse camera would need located and hook up that hot wire directly to the reverse camera power wire and perhaps ground the ground wire on the camera directly to the frame or ground it to the post of one of the rear turn/tail light fixtures. That could save having to buy another set of trailer lights right away. What do you think? I have bookmarked the suggested J-box kit and the wire in my browser pending your response.

Robin H.

6/24/2026

@Dave if you don't really need the reverse lights it can power the camera directly that is fine. That would also mean a single wire running back so you don't have to run multiple or do any splicing. You could also do that for now and if you change your mind, or find lights you like, add them later and then splice in on that circuit to run power wherever you need it.

Dave

6/25/2026

I found out that the 7 way upgrade kit does not appear to be in stock and will not appear to be available until the latter part of July. So I will wait awhile to attempt to order it.

Dave

6/24/2026

Or perhaps 12 gauge versus 10 gauge if the the 14-16 is too light and prone to voltage drop for reverse light circuit. Your further input on the gauge of wire is appreciated.

Robin H.

6/24/2026

@Dave I'm sure you would be fine with a smaller gauge like # 12-1-1, the 10 gauge just covers everything for sure so that was more of a catch all. It really just depends on what you have back there and the power draw. If you end up with LED reverse lights they use almost nothing, so you're down the camera. Most of those cameras run off running light circuits which will be a smaller gauge wire in the 14-18 gauge range but you also have to figure trailer manufacturers do the bare minimum to get things to work.

Robin H.

6/24/2026

@Dave I'll answer your tinned wire question here as well. It is just copper wire. Not a major concern if insulation remains in tact and you use quality heat shrink butt connectors. As far as I know we don't carry any wire like that, so you would have to pick that up locally if you want to use it.

Dave

6/24/2026

I only see either 14 gauge or 10 gauge in the blue wire. I'm thinking if for now I just run the single blue wire directly to the camera I could likely get by with the 14 gauge to save some money. Not sure existing trailer wiring is any heavier than that but it doesn't have the reverse lights on the circuit. Though I would likely get the suggested kit at the same time to try to save a bit on shipping. I'll try to double check with Camera mfg. to see what the amp draw is if I can get that and go from there depending on what I find out. So I'll wait a bit to order a kit and wire until I get that info. I believe I have a phone number I can call on that as well. Will post back what I find out. Thanks!

Dave

6/25/2026

@RobinH Robin, on the 7 way review video it was a little hard to hear what some of the colors represented in terms of what wires go to those connection points. I was wondering if there was an installation sheet with that info listed on your website. Now it's been awhile since I ran the wiring harness for the 4 way flat and the color coding may be different for the 7 way connector when using a junction box kit at least, but I'm used to 12V being positive and negative and represented in terms of red and black. Having said that is appeared in the review that black was for 12V power so given that's an opposite of how I generally looked at 12V can you suggest why black is used for 12V power and red for turn signal? Guess it's an industry standard thing or something but just curious on that. It could be helpful if I had a written instruction given I'm going from 4 way flat to this 7 way so I can review the colors of what I have and their functions ahead of time to insure I will be confident of getting the correct existing harness colors/wires and their functions installed on the correct locations in the J-box. Further for example on the 7 way the yellow appeared to be reverse lights and typically blue is suggested to run for reverse lights. Hence some confusion and how an instruction sheet could be helpful.

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Trailer Connector for Trailer With 4-Way To Add Reverse Lights

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