Undercarriage & Reversing Lights w/Wireless Remote

[A-Texan]

I completed another project not too long ago, but hadn't had time to post it till now. A while back I added undercarriage lights on my travel trailer and soon after a wireless remote and so far it is holding up well. Basically I wired into the reverse light circuit in the 7 pin (the wire was just blanked off in the junction box beneath the frame rail so it was easy to wire up), and then I spliced into the power side of the circuit with a wireless relay I bought online which allows me to use a remote similar to a car alarm remote and a wireless switch inside my trailer as well to turn them on and off. This really helps when setting up at night and when backing into a spot while dark as well. Here is what I did and what it cost below (except for the self-tapping screws, zip ties, heat shrink and rosin core solder, because I had that left over from other projects).

Total Cost: $107.98 + tax

4 LED Lights $32.38
Wireless Remote and Relay Kit $22.96
Fuse Holder $5.99
Marine Wire (50ft) $36.99
Electrical Hole Assorted Grommits $4.38
Plastic connector wire retainer/protector $0.28
Small box of 10-12 gauge connectors $5.00




1st I removed my battery box, inserted the relay where it would easily fit, measured out the wire from it to the electrical box beneath the trailer frame, installed one inline 7 amp fuse, and two terminal ends (one to be bolted to the frame as a ground and one to go to the power wire off the circuit breaker).

2nd I found the reverse lamp wire in the 7 pin harness which goes to the elecrical box (bottom right harness) and it was just sitting there with a cap on it not being used, so I soldered my power output wire from the relay to it and a power wire from there to all 4 lights I installed (two in the back of the trailer and two near the front of the trailer). From the electical box to the back of the trailer I used the marine wire (white one bottom left) because it has extra insulation to protect it. I basically ran a long piece all the way to the back of the trailer along the frame rail and then spliced two wires which run to the opposing frame rail for the lights on the other side of the trailer. See box below (notice while I ran the marine wire (white one) through the relief connector at the back of the box, I ran the relay's output power wire through the front plate; therefore, I drilled a small hole in it and used a grommit to protect the wire from the sharp edges).

3rd I grounded each light to the trailer frame where I bolted the lights down to secure them (so basically you are only running a power wire to each one, which means both wires in the insulation of the marine wire are carrying power to the lights, red wire to the right side lights and black wire provides power to the left side lights).

4th Installed the switch in the trailer and tested it out, lights worked, and then I hooked up my SUV, put it in reverse to verify they come on when in reverse and they did. Hardest part was laying under the trailer and cable tying the wires to be sure nothing was hanging down.

 

[Rich W.]

A lot of work but worth it because there is no such thing as too much light when backing in the dark. I put a big spot/flood on the rear roof of my coach for that reason. It may be a bit obnoxious when I light up the night, but at least I can see what I’m doing, and it doubles as a work/play light.

 

[DennisT]

Nice write up on the how etc you made the updates!

Looks like it would definitely help when setting up in the dark.

 

[Jim]

Excellent write up! Enjoy your new setup.

 

[mjeds]

was just thinking about doing this myself especially around the wheels for lights if I need to change a tire in the dark.

 

[A-Texan]

Thanks all, the first two trailers we had we just used an old spot light you can plug into our 12 volt recepticle in the car and one person would shine it out of the window while the other drove, but by my third trailer I wanted something that I could just switch on by myself to setup when we arrive late (it seems like we frequently arrive at places in the evening when its dark the last few years, I probably need to plan better, but we love stopping at random places while traveling to our next destination and we just spend as much time as we want between transit points). This last trailer I am adding all the features we would have liked to have had while using the first two (first was a really old trailer where I got a lot of my newbie mistakes out of the way and believe me, I made plenty of mistakes with that one so I am thankful we didn't get a new trailer first, the second was very well built, but smaller and really basic, but it was super cheap, while the one we have now was double the price of the last one, but it is a lot nicer). My next project is to install the backup cameras and generator on the back of the trailer, and I will be starting that over spring break in a few weeks.