Well, after months of complaining I can't see squat while backing up my 39 foot 5er, I decided to finally do something about it.
The back up lights that came with the trailer work but do not illuminate with any brightness my surroundings at night. They are there only to warn others you are in reverse. I went out to Pep Boys and bought 2 low profile 55 watt halogen fog lights for around 30 $ and a Bosch relay rated at 30 amps some 12 gauge wire and I already had some solder, a soldering gun, and basic electrical skills. I also picked up a back up alarm piezo beeper from Radio Shack at the same time.
I scoped out where and how to mount the lights which I wanted under the rear bumper and bent up some 1/8 steel brackets to mount my lights to. Then, I mounted the lights. Perfect, they look great. Next, to find the back up # 12 feed wire to the back up lights. I ended up pulling out the back up light out of the bumper which allowed access to this jumble of wires in behind the rear cap. I found the wire that feeds the back up lights and soldered another wire to it and ran that wire into the rear of the trailer in a small compartment and mounted the relay there. Fishing that wire into the small compartment was some work but not too bad. I use that wire to trigger on the relay. Next, I had to run a wire from my 12 volt panel out to the rear of the trailer and cover it all in wire loom and cable tie it into place.
That was a real pain, pulling off the underbelly and routing that wire. In retrospect it would have been better to run a 10 gauge wire rather then a 12 gauge wire I originally ran because I later added some more lights and 10 gauge wire would run all the amps I needed without having to run two feed wires and take up another unused 12 volt slot out of my panel. Now to label the fuse and install a 15 amp fuse along with a spare fuse in an unused 12 volt accessory location in a cabinet in the bathroom where all my 12 and 120 panels are located.
Now it's onto wiring the lights and the relay. I couldn't find a neutral wire anywhere convenient so I, under the rear of the trailer, found a suitable location and put in a white wire to the frame and ran a wire up to the relay through the floor along with another wire from the frame to the negative side of the lights. The trigger wire from the existing back up lights goes to the + side of the relay coil.The white wire to the - side of the relay coil. A yellow wire output from the relay to the + side of the lights and the Positive source wire to the the moving pole of the relay. All wires are wrapped in 1/4 loom and all connections soldered and covered with heat shrink tubing. The waterproof piezo beeper is in the same circuit.
I went out and hooked up the truck and put it in reverse. WOW!!
I lit up the whole yard with those lights and others can hear you backing up. It's necessary to run another + wire on another fuse so you don't blow breakers by using some unknown feed wire and the relay is so you don't overload the trucks back up light circuit with so many amps of additional draw through your back up switch. In essence, I'm just powering up the relay with the truck power but the additional lights are actually powered by the trailers 12 volt power system. What a difference, It worked so well I did it all over again and put in additional lights I can turn on from inside the truck on the sides of the trailer facing back.
Now, I have 220 watts additional lighting around the trailer for backing up into those dark camp sights after dusk and a back up alarm to alert small children and others that I'm backing up. What a great addition. It was certainly worth the effort. On a side note, at the same time I ran a number 10 wire from the battery through a relay that's triggered from ignition on back to the 7 wire connection in the truck to better charge the batteries in my trailer and installed another relay and back up lights on the truck also. Now when I put it in reverse for any reason I can see for a radius of 100 feet+ behind me giving me some added confidence I'm not going to run into that rock or the water hose bib that before this was all but invisible.
Paul R. Haller