Getting 12V power from your trailer plug is an easy way to power up your electrical devices on the road.
Luckily, with a 7 pin connector, your truck is ready to provide constant 12V power. You just need to know how to tap into that power.
This post goes over how you can tap into that power easily. It will go over, step by step, how to get power, including:
- Where is 12V power on your trailer plug
- How to get the connector to work for 12V power
- How to manage your fuse and the safety of an electrical component
Table of Contents
12V power
When you look at a wiring diagram for your 7 pin plug, you will see trailer wire for things such as your trailer lights, your trailer brake, and back up lights. All these wires are great for functioning the necessary power to each light or brake controller. But what if you want 12V power you can tap into to do the things needed while working with a tow vehicle?
If you look deeper into the diagram, you will see a red wire, also called a charge wire. This wire provides constant 12V power to your connector from your truck battery. You don’t need to turn on your truck to get power at this wire. As you need 12V power direct from your truck, this charge wire will be the main focus.
To get power, the basic rules of battery power still apply. You will need a positive (charge) and a negative (ground). Since the charge wire is positive, the ground is the next wire we need to find. The ground is a white wire on your wiring and trailer plug. This can be confusing as most truck batteries have the black color as negative or ground. Just remember that it is different for trailer wiring and the white wire is the ground. And the black wire is for your backup lights on a wiring harness.
Connector
Look at the photo below to get a sense of where exactly the charge and ground wire are on your connect. The trailer connector noted as number 3 white is your ground location, and the pin noted as 6 red is your charge wire location. As you look to get that 12V power from your truck, these are the wires we want to focus on your 7 pin trailer plug.
Knowing the location of your trailer connector, you can now proceed to get that 12V power from the trailer plug. I suggest you get a separate 7 pin connector and dedicate it to when you need 12V power. There are a couple of options when getting power from your trailer plug. You can either hard wire, meaning a direct connection to whatever you want to power. Or, you can put a 12V socket at the end to plug in 12V accessories.
If you don’t have power at your connector, visit my post on troubleshooting that problem.
How To Wire – Step By Step
Here is a step-by-step guide to wire your connector for 12V power:
- Step 1. Unscrew the set screws holding the wire and plug end in place. These are different size screws, so you will need a couple of different screwdrivers.
- Step 2. Find the charge wire and ground wire pins. Look at the pin diagram above if you need to.
- Step 3. Connect one wire to the charge wire location and one to the ground location. Make sure to use a thicker gauge wire. Depending on what you are powering, you can generate heat in the wire if it is not thick enough. Also, the wire length is a factor. The longer the run of wire, the thicker it needs to be.
- Step 4. Resecure the plug and wire set screw to the connector.
- Step 5. Put on a 12V plug end or wire the power you want.
They also make a pre-wired Trailer connector to 12V socket. You can also buy one, cut the 12V socket off, and hardwire your electrical components.
Fuse
Another thing to consider when using your trailer plug for power is to add a fuse. Your truck likely has a fuse for your auxiliary power at the connector. And if you exceed the amp rating of that fuse, it will blow a fuse, and you won’t be able to get power from your trailer connector until you replace it.
If you are going only to power small electrical appliances, you should be OK with just having the truck fuse. However, if you are going to power some hefty components, such as a winch or a power inverter, I suggest the following:
- Step 1. Go to your tow vehicle and open up the fuse box. You should see the relays and fuses for the truck. If you can’t locate it, look at the fuse panel, which is usually labeled.
- Step 2. Check the AMP rating of the fuse. This could be 10 or 20 amp fuse. Compare that with your power requirements on what you plan to plug in.
- Step 3. If your component to power is over 75% of the rated fuse (for example, your fuse 10 amps and what you want to connect is 8 amps), I suggest you add an inline fuse to your trailer plug. Add the same amp fuse as your truck fuse.
Adding an inline fuse to your 12V trailer plug will help in a few ways. The first is that replacing it will be easier since it is not under the hood and in a fuse panel. Secondly, if there is an issue, the fuse closest to the electrical component will burn out, and you can check more quicker. And lastly, if you use your tow vehicle trailer plug for other things, such as towing a travel trailer, the fuse will still be good, and you can plug in other trailer connectors and still have power. You can even charge your trailer battery from your 7 pin.
Final Thoughts
With the right trailer plug and knowing which wires to connect to, you can easily get 12V power from your trailer. You can safely power any 12V device you like by checking on your fuse and staying below max amps. Lastly, if you use your truck battery for power, you can drain a battery fairly quickly. If you have a large power-consuming device plugged in, you may want to keep your vehicle running, so the battery doesn’t drain.
Tony is an avid camper and RV traveler. He fell in love with camping on his first RV trip with his wife over 25 years ago. Tony loves sharing lessons learned and tips about RV maintenance and safe traveling.