Trailer Lights and Wires
On new trailer builds, and on existing rigs, the trailer lights and wires must all function. Here are some tips on the subject so if you find electrical a little confusing or intimidating, read on. This post is all about wiring up for success on the road.
There are lots of great options in trailer lights these days, but little has changed in wiring. Still it can be a little confusing, so hopefully we can unravel some concepts and make it easy to do it yourself.
Yeah, sometimes dealing with electrical things can be a little daunting. So many choices, so many ways to do it. Yet, it’s fairly straightforward when you understand the basics. Let’s look at wiring now for trailers.
In current times, there is almost no reason to go with anything but LED lights. Even if you’re replacing one on an existing trailer, it’s very likely you can find one to fit in the same form and bolt pattern, but in LED. (LED is Light Emitting Diode, in case you wondered. It’s just a lower energy way of creating brighter light. The are also much more durable — which is nice for trailers.)
The technology with LED’s has come of age. For new builds, you can get some really slim and very bright lights. We recommend sealed and submersible for everything because they’re only a couple bucks more. Of course your trailer may never go underwater, but if the lights are submersible, then you’ll never have to worry about corrosion or internal moisture damage that can make lights stop working.
Connectors – Hitch to Trailer
Oh boy! There are a ton of different styles of trailer electrical connectors. From 4-Pins to lots. 4- & 5-Pin flat and 7-Pin RV style are the most common for non-commercial applications, and I’d say if you have the choice, go with one of these. Our Trailer Wiring Diagram page has all the pin and color codes if you want them.
Connectors are more than just a lump dangling on the end of some wires. The trailer lights and wires depend on that connector, so make sure wires are soundly attached internally. Connect each wire securely, and button them all up well.
Button it up?
Yeah, Button it. Here are some tips (some controversial). Use what you like, discard the others.
- If you’re connecting wires to lugs, like in a 7-pin connector, spray a little PAM or WD-40 in there AFTER just to keep moisture at bay.
- Loose Wires can connect in a number of ways. The guillotine style ‘T’ connectors (shown blue) are popular, though some people say they’re trouble after a few years. I personally prefer Solder then Heat Shrink, but that’s harder to do on a ‘T’ in connection. Butt Splice Crimp Connectors also work.
- For loose wire connections, use electrical tape. Are You Kidding?? Don’t EVER use that – at least not by itself. Truth is, electrical tape makes a reasonable seal around joins AFTER you electrically connect the wires.
So, connect with solder, or Butt Splice, then wrap with electrical tape and finish with a zip tie around the last end of the electrical tape. Yes, that’s belts and suspenders, but it solves wiring problems.
- Make the wire connections staggered. When multiple wires are connecting in the same general area, make them different lengths so the connections stagger slightly. (See the photo above.) Wrap them separately (with electrical tape – not done in the photo) for isolation, then wrap them all together for final sealing.
- Use flexible conduit or some other flexible housing over the wires to protect them from the trailer to the vehicle connector.
A small version of the map (or wiring diagram) is shown here. It’s a typical Trailer Wiring Diagram / Schematic for most trailers. Click for the complete Trailer Wiring Diagrams article where you’ll find the full size diagrams and a ton of other information about trailer lights and wires.
We recommend one of 3 standards for wiring. They are all discussed in detail on the Trailer Wiring Article. Follow the standards. Don’t just pass off the trailer lights and wires thinking that you’ll be the only one that ever uses it. Sure shooting, you’ll want to pull some other trailer or you’ll get a new vehicle and have to mess with all the wires again. In this case, standards are good.
From the wiring diagram, use the wires that are applicable, and just leave out the rest.
Once you know what functions to include, just lay out the lights and wires. Starting at the front, measure the lengths of wire, then add for some extra, and get the parts.
Get the Needed Trailer Lights and Wires
All the regular trailer electrical parts are easily available either at your local trailer supply store or online. For lights, I’ve found that some of the online sources have a much wider variety than the local shops. Try eTrailer.com for instance, and do a search for the size and type of lights you want. Other places like JohnsonTrailerParts.com can get something that meets your needs.
For other supplies, I’ve actually found that the local stores carry the right pieces most of the time. Things like brake controllers, for instance, because they can help you get just what you need for your vehicle.
Tips For Building
When building a new trailer, dry fit all the trailer lights and wires to the trailer frame before painting. Add any holes for access or for mounting before the paint. This keeps you from needing to cut or drill into the beautiful new paint.
Hang wires from the decking (if it’s wood) rather than the trailer frame. Why? It avoids having to drill or tap into the metal frame. Also, it’s simple and easy to use a wood screw into the underside of the decking.
For a more advanced look, use conduit or tube to house the wires.
Or another option is a lot of wire hangers — like this rubber wrap P-Clip. (This image is looking up from under the trailer showing a routing support clip on the underside of the deck.) In this case, a groove in the bottom of the decking allows the wires to easily pass over the cross members without pinching. It’s a protected channel just for the wires. P-Clips like this one secure the wires between. (Just don’t forget to disconnect all the wires before replacing the trailer deck!)