Bought a really well made trailer. (I won't post the company here, because I'm pretty sure this isn't their fault and I def. do not want negative press for them, they are awesome!).

Pulling with 2016 Heritage.
Running LED headlight/passing lamps, so lower power draw already.
Trailer is wired for 6-wire. Left, Right, Running, Brakes, Ground, 12v power. (Using this configuration.)
Using this harness, in the 5-wire option.
Using this 6-pin connection on bike.

Vendor put the trailer on my hitch and plugged it up. (I checked, very tight connection.) We tested blinkers, brakes, running lights. He immediately says "those lights should be brighter than that, you need to make sure you have 12v running to them." When I did all the harnessing and wiring and mounting, etc., after I was finished (and multiple times before), I used a multimeter to test the various functions and got 12v on all the actions.

Is there something I need to do to my bike to handle the extra "load" (resistance?) with the trailer hooked up? I know I have it wired right (I'm a programmer, and this is well within my abilities to handle and test). With the lower draw of a LED headlight, I should have ample power available for the trailer lights.

Would appreciate any input y'all can offer.

 

Have you checked your battery AT THE BATTERY with the engine running? With meter probes on the battery posts should read about 14.3 v with engine idling. If not, check battery connections and ground connection on the frame. Check voltage regulator connections.

 

Besides the metal hitch itself, do you have a ground wire (12vdc neg) between the bike and trailer light circuit?

Are you testing the trailer lights with bike off or running?

If off; Battery getting weak?

Test ground on trailer to neg of lights on trailer.

If your battery/alternator , bike lights is/are good, then start looking for poor connection(s) at trailer.

If you have a known good spare 12vdc battery (car, lawn tractor,boat, UPS, etc) you can unhook your bike and just eliminate that.

 

Thanks for the input, guys. I'll check these. I do have a ground wire, it's part of the 6-pin schematic. (I might separately ground it, though, just in case it's not grounding well through the harnesses, that should be okay to do.)

I pulled the trailer for about an hour, stopped for gas just before getting home (I hate having an empty tank) and was able to restart, no problem.

 

My 2cents are on a poor ground on the trailer itself. Loose/corroded ground lug somewhere. Sockets (the grounds) for bulbs rusty maybe? Loose crimp on a wire.
After trailer lights have been on a while, feel around the trailer wiring with your bare hands for heat.

If your lights are ACTUALLY really dim, then the voltage drop across a poor connection is heating up something somewhere. Could even be a wire that's got pinched and some strands are broken inside of the insulation.

 

Definitely not corrosion or rust. This is a brand new, made-to-order trailer. Shiny!

The manufacturer (solo operation, mostly), assured me that he used his test rig, and when he did, the lights were far brighter. I'm putting my money on my harness some of the 6 pins (in my harness) having a bad connection. I'll start by just doing a completely separate ground, since so many folks have suggested a bad ground as the first thing to check. I haven't hooked it back up since I got home. In fact, I hadn't even ridden my bike again until today. Been like 2.5 weeks! Wife has been recouping from totaling her bike...fractured knee, busted nose, so doctor's visits and nose surgery and physical therapy. Just been easier to have the truck and come home at lunch to make sure she's situated. Bought her a walker, heh, and she's been hobbling around a little better, though she can only use the one good leg until the brace comes off in another 4-6 weeks. Been hard to get out and play with the bike, ya know!

 

Eliminate the bike altogether and stick a 12v lawn tractor (or other) battery onto your wire harness on the trailer and report back.