Best practices for trailer electrical wiring

If you're using the body for ground, make sure it is welded well. Run a separate ground wire from the trailer side of the plug to the body. If the body and frame are separate, run a ground to the frame, too. I like to solder crimp terminals on trailers because they get so much vibration, so I run a bit of extra wire through the crimp barrel to solder onto the lug. Just do it quickly with a hot iron so it doesn't wick back under the insulation and cause a premature failure.

Wire is cheap so, I usually run a ground wire all the way back. It's an Anti-Lucas clause I've always had in dealing with electricity. I used to weave my own harnesses, then wrap them with black tape, when I worked at the body shop. There was lots of harness repair for me there, too.

-- Always bear in mind that your own resolution to succeed is more important than any one thing. -- Abraham Lincoln

i doubt there are firm rules. For me number one is put everything in conduit, number two is no daisy chaining (run a separate wire to each light and each brake from your central junction box at the tongue)I also silicon seal all the crimp connections by putting the silicone in before crimping and then wiping smooth.

I did this on the trailer I bought 22 years ago and sold last year. Never had a failure the whole time.

Karl

Do NOT use the vinyl covered wire sold for trailer lights! The vinyl attacks and corrodes the copper wires inside, and will turn into junk in a few years. Use 16-3 SO wire, a separate wire to each light, and use one wire for ground, and one for tail and one for the signal light.

Never use the frame for a ground. Total waste of effort. over the next

50 years..

Sounds like a great plan Karl. I will try to follow it.

Dod you use ground wires also?

i

Yep, "anti-Lucas", I hear you ...

i

the conduit was the ground run. Wires from each device bonded to it. Might have been easier to use more wire.

Karl

What Karl said, but with PVC conduit and ground wires. A tube of dielectric grease is handy too - dab on things to keep the water out where stuff plugs together.

that would work well if it fits the weather tight junction boxes. I didn't mention I use rubber gas line hose as the conduit to the brakes. It has to flex. Also silicone every place that might possibly leak.

Karl

Set down and plan out what you want for lights and if you want any extras (like on board power for a winch or maybe a couple of detachable work lights or deck lighting) I just rewired a 20' beavertail last month and it now has control sockets at both ends for the winch, deck lights at the front and dual S/B/T lamps at the rear. Plus back-up lamps. Works MUCh better if you can run all the wires and then seal it up.

Does it have a wiring box now? If not then plan on starting there. You want a weather-tight box that you can run conduit out of. Inside this goes a couple terminal strips. This allows you to easily connect the pigtail (and replace it as needed) and run wiring neater and easier. Out of the box you will be running conduit back to the tilt pivot. Here you add a section of flexible watertight conduit to a box on the tilt frame. Out of that box you run conduit as needed to reach each light/accessory. OH the conduit doesn't have to be EMT. I use different items for different lights. For instance I like 1/4" brake line tubing to the marker lights. Easy to find, easy to clamp and bends real nice. Run the wires through it prior to bending as it makes it much easier.

For ALL connections you will want to either solder, coat and shrink tube OR use heat shrink self sealing crimps WITH THE PROPER CRIMPING TOOL!!!. ALL wires get matching grounds. I don't use the frame for a ground as rust likes to screw around far to much. I do run a ground to the frame just to eliminate static potential though. I HIGHLY recommend LED marine safe lighting items. They are sealed, last a LONG time and use much less current overall. (this can cause problems if your tow vehicle has mechanical flasher elements so I also install an electronic flasher and hazard unit on my vehicles.

I prefer TFFN to the flat wires. I wrap them in Scotch 66 tape to keep them together, and add some extra protection.

I like to use one of the three or four foot extensions so I can replace it in a hurry, or remove it and conceal the trailer's connector when I have to leave it somewhere. It's less likely to be stolen if they think it's defective. :)

I used 3/8" CPVC pipe to each of the lights on my last trailer, along with a PVC waterproof electrical boxes & covers. I used 1/2" Schedule

40 conduit between the boxes, and reducers for the CPVC. One box near the tongue, and the other at the rear, under the frame and out of sight.

Karl, I've become somewhat skeptical of silicone. There are so many things that are do much better without the downsides.

YMMV, of course.

But I refuse to automatically slather silicone goo on things anymore.

Especially the acetic acid catalyzed stuff, corrodes metal all to hell.

Drive-on boat trailers for salt water service are a special case, I guess. At the first sign of trouble, I just pull all new wire and replace the lights, so for that case a simpler installation is better. Still, I've gotten 10 years with the original setup, don't know about the new led's. They might be even better. By then, I'm usually replacing springs and/or axles anyway.

One practice I try to follow is to unplug the lights before backing in. The other is to try to remember to plug them back in before hitting the road. That one's harder.

Pete Keillor