I had the opportunity to show off my wiring expertise on a construction worker’s trailer. The first thing I did is was to access how much parts and labor I would need for this project so I could give the owner an estimate for my work. He wanted me to go ahead with the work.
So I started on the trailer and I got out my floor jack and jack stands raised it high enough for me to crawl underneath it and make a list of tools needed for the project. I made a list of the tools I was going to need.

placement of my jack & jack stands.
- Wirecutter/wire strippers
- Flat tip number one screwdriver
- Number 2 Phillips Head screwdriver
- Box cutter or razor blade
- Pair of wire dykes
- 14- 16 gauge crimp connections
- 4 wire nuts
- Protective wire wrap
- Rubber insulated clamps
The owner supplied me with the wire harness and the light set he wanted on it. So next for me to do is get under the trailer and start ripping out all the junk wiring and unused wiring from this trailer and wire in all the new stuff.

Junk wires ( unused)
Next, I laid out all the new wiring and installed the rubber insulator clamps in the location of the old hangers. Then I moved on to installing the taillights & boots. While installing the taillights, I wanted to be sure I put on my protective wire wrap over the wires and run the wires to the taillights where they wouldn’t be hanging down and in a proper area where the wood in the bed of the trailer and the steel of the frame would not rub on the wires.

Taillight boot w/boot. and wire connection.

New taillight and its connection.
Once I have the wires where I want them to go to my lights, I finish running my wire wrap up to the tongue of the trailer. After that is on I take the rubber clamps and install them around my wire wrap and be sure that nothing is hanging down once the hangers are installed.

Boot install & wires ran into trailer left rear corner.

Plugging in the wires.

Rubber Insulated Clamps

Driver side installed
Now I install the 7-way RV plug connection at the tongue. Once we are at the tongue I use the box cutter (or razor blade) to cut away at the black installation so I can get access to the wires in the harness.

Box cutter or razor blade to cut back the wire insulation to access the wires.

Cut the insulation back to get just enough wire to connect to the plug.

Wire cutters to cut off the excess insulation.
Take a look at my trailer wiring diagram sheet and it will aid in knowing where each wire goes in the plug connection. We will also use this for the taillight and side marker light connections.

The trailer light wiring diagram will help me wire everything correctly.

wiring diagram
Now we’ll wire in the new plug at the head of the trailer. When installing your wire harness into your plug, loosen the 2 screws in your trailer plug housing. One screw holds the housing together and the other screw holds the whole harness inserted in the plug housing. You can tell the difference because one is at the BACK of the plug and the other is in the FRONT of the plug connection itself.

Front Screw to remove to access the plug connections.

The rear screw is to be removed.
Before stripping your wire harness, feed it into your wire plug housing first. You may need to lube the white silicone boot so it will make it easier to feed your harness first. Once the harness is fed into the housing it will push out the plug connections in the housing.

When this connection’s head is pushed out! then you can connect your wires to each post.

the plug is being pushed out with a wire harness.
The plug connections are where you’ll connect your wire harness to. Once the wires are through strip just a little bit back on each wire. Have the wiring diagram close by so you can read off of it.

one wire at a time is my suggestion.

each wire has its place follow the instructions.
This is where the fun begins! Following the wiring diagram, it will indicate where each wire goes from the notch in the head of the plug connection where each wire goes and be patient while doing this because when working with electrical you won’t want to do it multiple times because you only have a preset length of wire.

Using the 1/8in screwdriver you can install each wire into its proper place.

Just Beautiful.
Once I have every wire connected to the plug I go and check my rear taillights and check for continuity from tongue to tail being sure current is visible. I had a little snag while doing the trailer. I had to go into access to the junction box and I found out a couple of wires were not hooked up at all. So I made sure they were reconnected and then I did the test again for current for each taillight. It all looked great!

Our wires were unhooked in the junction box.

So much for a perfect current flow.

Inside our junction box, a coupe wire was unhooked.

some wire nuts fixed.

the man who fixed the wires in this trailer.
So I backed my truck up to it and did a proper test while being connected to a vehicle. We have lights!!! Victory Cruise!!