Oh So Electric! Vintage Trailer Wiring, the Basics

What NOT to do in trailer wiring.

At the start of my vintage trailer obsession, I was really terrified of anything electrical. Electricity to me equaled electrocution, so I wouldn't touch it. It was also really confusing! But once I did the demo for my first crazy frame-up restoration, I noticed that the electrical system in vintage trailers is actually quite simple.

After watching a few YouTube videos (I have included the helpful ones down below), I got super excited about rewiring my camper! Please keep in mind that I am NOT an electrician, and am NOT trying to give advice of any kind on the actual process. I'm just attempting to explain the basics and then giving you resources from the pros (the qualified experts). I still have not yet tackled rewiring, but at least I can help you understand it.

The electrical system in my trailer reminds me of the route I take for my weekly shopping errands. Bear with me for a minute here. For my errands, I drive my car from home with money to do my shopping. I stop at the pharmacy, pick up prescriptions in exchange for money, then on to the pet supply place down the street. Stop in, pick up dog food in exchange for money, then drive to the hardware store a block down. Pick up trailer parts in exchange for a lot of money, then change direction and head to the grocery store that is a few blocks from my house. Get groceries for the week in exchange for even more money, then drive home. At each stop, notice I leave money in exchange for goods.

My car represents electric current. My house is the source of power. In a camper this will be either a battery, or "shore power" (a marine term meaning plugging into power at a campsite). My route are the wires in the camper, which make a loop around town from my house then back to my house at the end. Each stop on my route is a fixture; either a light, a fan, the refrigerator, and whatnot. My car (electric current) drives the route (wires), stopping at each place (a fixture like a light), leaving money (current) and getting goods (power to the fixture which causes the light to turn on, fan to run, etc.), then returns to home again (source of power). That describes a circuit.

Add a switch on our route at each location (fixture), which interrupts the flow of electricity to the fixture. When the switch is "on", electricity flows to the fixture and the light is turned on (I can go into the location and buy what I need). When the switch is "off", the flow of electricity is interrupted to the fixture so the light is off (the location is closed and I can't go inside to do my errand.

To clarify, the electricity is not "spent" when it is delivered to each fixture. It is just transferred into a different form of energy at each fixture, such as light or air from a fan. Like I trade money for my purchases. Hopefully, that makes some sense to you.

Electrical Systems in Vintage Trailers

There are typically three electrical systems in a vintage trailer. Two of the electrical systems were created for the interior of your trailer, and one for the exterior. We are not going to address solar in this post but usually that will be tied into one of the interior systems.

The two interior electrical systems account for the two different situations you might find camping; either 1. having electrical hookups at a campsite (electricity) or 2. camping without hookups (battery power). The third system is only for the exterior of the trailer, to run brakes, brake lights, turn signal lights and running lights on the exterior of your trailer. This is run on your vehicle power's through the connector on the hitch of your tow vehicle.

AC System

Let's talk about the first interior electrical system, the AC system. This is used when you plug your camper into an electric hookup at a campsite and take their power to run lights, etc. You need to make sure you have the proper connector to plug in to the electrical hookups. Typically, older trailers will have a 15 Amp capacity unless they are upgraded. Many campsites have 30 or 50 Amp connections, so you might need an adapter if that doesn't match your trailer. For example, you might need a 15 Amp to 30 amp adapter if your trailer is 15 amps and the outlet is 30 Amps.

The AC system can power things like some of your lights (110 V), a microwave, phone charger, a fan or other small appliances. These little trailers are old, so most of them don't allow you to run much as-is. Their systems just don't allow enough power into the trailer for modern appliances unless they are upgraded. To figure out what appliances you can use in your trailer, aside from what is already there, you should check out this calculator. Many old camper refrigerators run on the AC system, but also run on propane because there isn't enough power in the DC system (battery) to run it. Personally I stick with what the previous owner was comfortable running. I run lights, the small refrigerator, a toaster, microwave, fan and phone charger (but not all at the same time) and they work just fine in my old 1966 Aristocrat Land Commander. Your experience may vary and it is easy to overload an old trailer so use caution.

To use your electric hookups, locate the power pedestal for your campsite. For safety, make sure the power is off by checking the circuit breaker on the pedestal to ensure it is off. Then plug your power cord into the trailer's inlet and ensure the connection is secure. Plug the other end of the power cord into the designated outlet or adapter, if using one. If you are using an adapter, make sure it is a secure connection on both ends. Now you are ready to turn on the circuit breaker at the pedestal. Check to make sure it is working by turning on a light or other fixture. Some people use surge protectors, between the power source and the trailer, to protect against a power surge. I think is a good idea but have never actually used one.

DC System

The second interior system is the DC system, which is when you do NOT use hookups, but still need to run lights, etc. The DC system is run off of a battery in your trailer. A DC system is also called the 12 Volt system, and has a much weaker current than the AC system, so cannot run some of the more power-hungry fixtures. This system usually consists of some of your lights (12 Volt), but might include a 12 V fan or other fixture,

Now, interestingly enough, some of your light fixtures are part of the AC system, and some are part of your DC system. Some of the more rare light fixtures will be connected to BOTH in the same light fixture, which sounds confusing but is really rather clever. One bulb is connected to the AC circuit and one bulb is connected to the DC system. There will be two switches, one for each system. This is when you have to be careful what type of bulb you put in which socket because a light bulb that works on AC will not work on DC and vice versa (and could explode, so I have heard).

To make things more interesting, there may be a battery converter, or battery re-charger, that charges the battery whenever you plug into hookups. This would be considered part of both systems as it converts AC shore power into DC power in the battery. Another option is to install a solar panel to charge the battery through a charge controller, which I have done on Trailer Mary Ann.

The opposite is an inverter, which converts DC power from the battery into AC power to run appliances, etc. If you ever want your battery to run more than 12V lights, you might want to consider looking into an inverter.

Exterior Trailer Lighting System

The third electrical system powers your trailer brakes (if you have them), brake lights, running lights, tail lights and turn signals. This system is powered by your tow vehicle through the wiring connector at the hitch.

Common connector types in vintage trailers include 4-pin or 5-pin flat connectors, 6-pin round connectors, and the more modern RV-style 7-pin round or blade connector. Many older trailers were built with 4- or 6-pin plugs, but upgrading to a 7-pin RV-style connector is really worth considering—especially if your trailer has electric brakes or you want the ability to charge the trailer battery while towing. The vast majority of tow vehicle hitch harnesses and trailers use 7-pin nowadays, and you will make your life easier if you do too. Funny, one of my old trailers, Trailer Ethel, had a 6-pin connector (which I had never seen before) and I had a heck of a time figuring out what to do with it.

Here’s a clear visual of a 7-pin RV trailer connector showing each pin’s function and typical wire color. Warning: Older trailers DO NOT always follow the wire color standards!

Rewiring a Trailer

Now for re-wiring! This is when I rely on the power of the pros: The cute gentleman from Mobiltec and Canned Ham Trailers does some excellent videos that demonstrate how to re-wire your camper. In fact, these are some of his best videos. He happens to be a staple in the vintage trailer world. I am including them below as a quick reference guide. Again, I am NOT an electrician, but he is! He has been at the trailer restoration game for decades, knows what he is doing, and gives really fantastic demonstrations. He even conducts classes, so look him up if you need more guidance.

I hope these were helpful--they were for me. If this still is confusing you, consult an expert electrician. Verify that the professional knows about trailer or RV wiring because it isn't exactly like the wiring in your home.

Safety Tips

1. Double check that you are NOT plugged into shore power or a battery before beginning.

2. Check the wiring and connections on each fixture as you go along to make sure they work. It is really frustrating to finish a whole trailer and have nothing that works. Then you have to test each one anyway!

3. Make sure all your connections are secure and won't come apart. This is very important!

4. Don't forget to connect your ground to the frame and the skin of your camper.

5. Always install a smoke detector and two fire extinguishers on your trailer (one outside, and one next to your bed) for emergencies.

Hope this sheds some "light" (insert groan here) on your trailer electrical systems.

Happy Atomic Trails!

Disclaimer

The information provided on this website, in videos, social media posts, articles, or any other materials is for general informational and educational purposes only. It is not professional, legal, or engineering advice. Renovating, restoring, or modifying vintage trailers—and towing them—can involve risks, including but not limited to structural failure, electrical hazards, fire hazards, and injury. You are solely responsible for determining whether any project, modification, or safety procedure is appropriate for your specific trailer, skill level, and circumstances.

Always consult qualified professionals—such as licensed electricians, plumbers, structural engineers, certified trailer repair specialists, or certified RV inspectors—before undertaking any work on a trailer’s structure, electrical systems, plumbing, or towing setup.

By using the information provided here, you acknowledge and agree that:

• You assume all risk for any injury, loss, or damage that may occur.

• The creators, authors, and publishers of this content are not liable for any damages, injuries, or losses arising from the use or misuse of this information.

• Compliance with all local, state, and federal laws, building codes, road safety regulations, and manufacturer specifications is your responsibility.

If you are not experienced in trailer restoration or repair, seek professional help before attempting any work. Safety should always be your first priority.