I purchased a kit to rewire my trailer and the instructions that came with the kit were not very detail so I decided to do this Instructables to help fill in some of the gaps.
Note: These steps are not meant to replace the instructions that came with the kit and you should follow all warnings and cautions that they may include.
Here is a list of tools and supplies that I used to complete the install. From left to right: Side cutters, 3/8 drive ratchet with a 7/16 socket, wire crimper/stripper pliers (these are not required if you use the wire nuts that come with the kit), four wire butt connectors (in replacement of the wire nuts), two wire taps (included in the kit), four 1/4 inch screws(also included), a drill with a 9/32 drill bit. Tools not pictured that I ended up using were a cross tip/Phillips screw driver and needle nose pliers.
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Step 1: Purchasing a Light Set.
When undertaking this task an important step is deciding what type of light set you will need. The trailer that I am re-wiring as no lights or wiring currently installed, so I need a complete kit. The kit shown is from Harbor Freight https://www.harborfreight.com/12-volt-led-trailer-light-kit-64275.html. It is a complete kit and has all of the supplies that you need to install the kit. NOTE: When selecting a kit make sure that is has enough wire to reach the length of your trailer.
Step 2: Installing the Tail Lights.
When installing the tail lights it is important to make sure that you install the correct light on the correct side. The lights that came in the kit were labeled left and right, but make sure that you are putting them on the correct side in reference to the trailer (standing at the back looking forward). The way that most vehicles are wired for trailer lights is the green and brown wires on the right and the yellow and brown wires on the left.
Using the ratchet and 7/16 socket remove the nuts from the back of the light and place the light mounting studs in the existing holes on the trailer. Before putting the nuts on, place the white grounding wire on on of the mounting studs. This makes sure that you light has a good ground. Tighten the nuts down.
NOTE: When tightening the nuts do not over tighten, the studs are held in place with plastic and thin metal it is easy to over tighten and break the mount. After installing one side move to the other and repeat the process on the other side.
Step 3: Running the Wires
Since this trailer has no wiring I need to run new wires for the lights. If your trailer already had wiring installed you can skip this step.
Take the wire harness from the kit and unravel the entire harness, as stated in a previous step it is important to run the correct wires on the correct side, run the green and brown down the right side and the brown and yellow down the left. Failure to do so will result in the trailer turn signals being opposite of the tow vehicle’s.
When installing the wiring make sure that you run the wire over the axle and as close to the frame rails as you can. Look for holes already predrilled in the frame, if there, run the wires through those holes. This helps keep the wire up out of the way and slightly protected. After running the wires make sure that the wires for the trailer match the wires on the lights. This just helps confirm that everything is where it should be.
Now go back to the front of the trailer and make sure you have enough harness at the front to connect to the tow vehicle. It helps to have the vehicle attached to the trailer for this but it not required.
Step 4: Connecting the Wires.
Use the side cutters to cut the harness to the proper length. Then use then wire crimper/stripper pliers to remove approximately 1/2 inch of shielding from the wires. Do this on both the trailer harness and the light’s wires.
Now this is where I deviated from the kit slightly. I don’t like to use the wire nuts that are supplied in the kit so use butt connectors instead. I feel that this is a bit more secure and provides a better connection for the wires.
Take the butt connectors and using crimper/stripper pliers crimp the connectors to the ends of the harness wires. Then making sure that the colors of the wires match crimp the other end of the connectors to the wires on the light. After they are crimped give them a GENTLE tug to make sure that they are connected properly. Repeat this same process for the other side.
Step 5: Installing the Marker Lights
One of the last step in the process of this project is to install the marker lights. This step is not required but since the kit came with them I decided to install them. First decide where you want to mount them. On this trailer the is a spot towards the front of the trailer that was close to the wiring harness and had a flat surface to easily mount the lights. After deciding where to mount the lights, mark and drill the holes using the drill and 9/32 drill bit. Now using the small loop connectors that came with the kit strip and crimp it to the white wire on the light. As you install the lights using the 1/4 inch screws and the cross tip screw driver run one of the screws through the small loop on the back side of the light and install the light on the trailer.
Now that the light is installed on the trailer you need to connect the brown wire from the light to brown wire on the trailer harness. It can be kind of tricky to get the wire separated, but just take your time and use the needle nose pliers to gently pull them apart. Once they are apart take and place the wire tap on the brown wire. Then, take the brown wire from the light and place it in the other side of the spice. Use the needle nose pliers to crimp the metal splice down into the wires and close the retainer clip over the top of it to keep everything in place.
Now that one side is installed move around to the other side and repeat the steps to install the other light.
Step 6: Operational Check
Wow, good job you are done.....almost. The final step in the process to make sure that everything works as it should. For this you will need to hook the vehicle that you are going to tow the trailer with to the trailer. Once everything is connected turn on the vehicle's headlights. Now walk around the trailer and make sure that all of the lights are on. If they are on then go and place the vehicle's turn signal on to one side or the other and go check the corresponding tail lights to ensure that it is blinking. Then repeat the turn signal test for the other side. To test the break lights you will need someone to apply the breaks in the vehicle while you observe the lights.
If all of the lights work and in the right spots you are done.
Thank you for taking the time to read through my "Instructable".
If you have any questions or feel that I left something out please leave me a comment and I will do my best to give you an answer.