Starting at the main wiring connector, trailer wire colors help us trace the conductors to all the proper electrical connections. The colors are specified by the various wiring standards such as the SAE ( Traditional ) standards, or the newer RV Standard for trailer wiring.
So, what is the big deal about trailer wire colors? A wire is a wire, right? Yes, almost. Certainly, the most important thing is the functions of what the wires do, like illuminating the correct lights. That happens by following the pin standards so the trailer connector we plug into our car matches the functions wired into the trailer.
Colors for the wire insulation are a good way we trace connections. This is how we know it will work with the tow vehicle it connects with.
Standards For Trailer Wire Colors
While there are many standards, and each has a purpose, we will focus on 2. These are the 2 standards that most cars and trucks are wired with from the factory. If your vehicle has a 7-pin trailer wiring plug connector from the factory, it is probably one of these. And, these are the same 2 standards that most trailers come with.
Interestingly, the 2 wiring standard are electrically the same, but differ only by wire insulation colors. (Don’t ask me why, I personally think it is ridiculous to make it confusing without a reason.)
Anyway, now you know, there are the 2 standards, but they both connect just the same. So, just make sure the wires of your vehicle and trailer are one of these standards, then even if they are not both the same colors, they will work.
Why Are There 2 Trailer Plug Wiring Standards?
That is a really good question for which we do not have an answer.
The SAE J2863 is the overwhelming standard for trailer wire colors with a 4-Pin flat connector. The 5-Pin flat connector is similar, and still follows the SAE standard. Read more in the Trailer Wiring Diagram article.
The SAE J2863 also applies to the 7-Pin Blade connector – with more wires. Functions by color are the same as the 4-pin and 5-pin, then more functions are added. This makes perfect sense.
In contrast, the RV Standard is different, and applies only to the 7-Pin Blade connector. (RV Wiring Plug as it is often called.)
In this article we will discuss the 7-Pin Blade connector – which is by far the most common – and it is the one with the 2 deviating standards.
(Note: There are other standards for other connectors, especially in the industrial realms. Some have round pins, some have blades. If that is what you have, see this post by Curt Manufacturing for help with wiring.)
Trailer wire colors for both the “SAE Standard” to the “RV Standard” are in the chart below to compare.
RV Standard vs. Traditional / SAE Trailer Wiring
For the 7-Pin BLADE connector – only the 7-Pin – there are 2 standards. First, the SAE J2863 (“Society of Automotive Engineers” also called Traditional), then Second, the “RV” Wiring Standard ( RVIA/NFPA ). The connections are the same, but the colors are different.
That means a trailer wired with the colors of SAE will connect just fine with a tow vehicle wired with the colors of the RV standard – and vice versa.
Personally, I think the RV Wiring Standard just adds confusion for no reason. The SAE Standard keeps the same colors for the main functions – consistent with the 4-pin & 5-pin flat connectors – which makes sense. Unfortunately, the RV Standard scrambles the colors for no apparent reason (like flipping green and brown). Stupid to add confusion IMHO, but whatever. They both exist, so we have to deal with it.
Hey, Electricity is color blind, so in the end, it is the connection that matters. Both standards connect the same, and use the same pins for the same functions. So is there a point to having 2 color standards?
Wires Of The 7-Pin Blade Connector
In reality, the actual connector pins are NOT numbered, but we show them with numbers here so it corresponds with the chart of trailer wire colors below, AND with the numbering we show in the Trailer Wiring Diagram article.
Here is the 7-Pin Trailer Wiring Connector with pin FUNCTIONS:
Trailer Wire Colors By Function
What is the color code for trailer wiring? In the table below, we break out trailer wire colors by function, and by the pin numbers above. (See the Trailer Wiring Diagram page for the 4-pin and 5-pin connector information.)
| Trailer Wire Functions By Connector & Color Code Traditional / SAE Colors – And – Colors for the RV Standard |
||||||||
|---|---|---|---|---|---|---|---|---|
| Connector Style | Pin | Function | SAE Color |
Description | RV Standard |
|||
| 7 Pin |
5 Pin |
4 Pin |
1 | Ground | White | Ground Wire for all trailer electrical functions |
R Vi s 7 P O |
White |
| 2 | Tail Lamps Running Lights Side Markers |
Brown | All normally ON lights. Tail, Running & Side Markers |
Green | ||||
| 3 | Left Brake Light Left Turn Signal |
Yellow | Multi-function signal for the Left Side Rear Tail Lamp |
Red | ||||
| 4 | Right Brake Light Right Turn Signal |
Green | Multi-function signal for the Right Side Rear Tail Lamp |
Brown | ||||
| 5 | Brake | Blue | Electric Brakes Control or (5-Pin only) Surge Brakes |
Blue | ||||
| 6 | Aux Power | Red* (or Black) |
Vehicle Power +12V Battery charging / Accessories |
Black | ||||
| 7 | Reverse Lights | Purple* (or Gray) |
Back Up Lights / Surge Brake Control |
Yellow | ||||
| * Note: Some vendors deviate by changing Red to Black, or Purple to Gray. Color deviations do not change the pins, or the function. See SAE Colors By Function In The Trailer Wiring Diagram Article |
||||||||
Colors are great to easily see what wire goes where. Consistency is also good – which is why we like the Traditional SAE Standard better. The first 4 functions have the same colors on 4-Pin, 5-Pin and 7-Pin connectors. That makes more sense to me because it is consistent.
In our trailer wiring diagrams we show colors for the SAE ( J2863 ) aka “Traditional” Standard. If you have the RV Standard ( RVIA/NFPA ), the connections are the same, but as in the chart above, some colors are different. Since the connections are the same, just color our diagram wires different and you will have the RV standard in a trailer wiring diagram.
SAE or RV Standard?
Which One Should I Choose For A New Trailer Build?
If you need more than the simple 4 functions, we definitely suggest using the 7-Pin Blade connector. It is the most common, and it works with both SAE wiring, and the RV wiring plug standard. (Just leave the unused terminals blank – if you only have 5 or 6 functions.)
What about the RV standard? All I can say is it exists, and this is the way many vehicles and trailers are wired. While the 2 standards only differ by the wire colors, the pin positions and functions are the same. That means both standards will work with the same tow vehicle.
Which standard should I choose? I suppose it does not matter, because they both connect the same, so choose your favorite, and wire your trailer that way. Personally, I prefer the SAE standard because it is consistent with the 4-pin and 5-pin connectors. That makes it easy to work with for all sorts of trailers, AND, the bundles of colored wires (the 4 main functions) are easy to get. However, if you like the RV wiring plug standard colors, go for it. The choice is up to you.
The 7-pin wire bundles are available in both standards. For example, you can find both on Amazon, readily available.
And while the exact standard does not matter, if you are building a trailer following one or the other can be very helpful when it comes to trailer inspection before licensing.
Trailer Wire Color Variations
All the wiring standards have colors assigned to functions, but that can be confusing because the colors are not always consistent. For instance, with the SAE standard we might see a Black wire instead of Red, or a Gray wire instead of Purple. That is not the best, but don’t let the color discrepancies confuse you.
We often see similar color discrepancies with other standards too.
If your colors do not match, then GO BY THE FUNCTION, NOT BY THE COLOR. That goes for all the wiring standards.
Wiring Your New Trailer – RV Standard & SAE
One of the tasks involved in building a new trailer is wiring. We have to set all the lights, run all the wires, and make all the connections. Some good tips for wiring are in the article about Trailer Lights and Wires. Even more tips are in the article about Breakaway Kits.
We will add one more good tip here for handling the wiring complexities with trailer wire colors. We recommend, If you can, then use a junction box.
With a good junction box, you can wire the trailer with the SAE standard, then buy and wire the connector for the tow vehicle. It does not matter if it is either the SAE or the RV standard. Even if it feels like mixing paradigms, when you make the connections in the junction box according to function, then you are good to go. Just use the chart above to match the wire functions.
If you get a trailer parts kit for one of our trailer plans, use the colors and functions as we mention above. Either standard works. If the kit does not have a junction box, ask them for one.
Mark or tag all the functions in your junction box. The marking acts as documentation so if you ever have a problem later, you will have all your notes about which wire does what. Again, label by function. That will definitely make it easier to work with later.
Good Luck with all your Trailer Wire Colors!
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