Trailer Wiring Troubleshoot

[DaytonaJoe]

So here's the story... I set up my Mazda 3 to tow a small utility trailer with a couple of kayaks and everything was great for a few weeks. Last week as I was driving out to the pond it started to rain. I checked the trailer's lights midway through the day and everything was working fine. A couple of days later, I discovered that the tail lights, brake lights, and turn signals no longer work. The side running lights still work, and the Mazda's lights are all normal. I took this to mean that it probably wasn't a fuse issue. The trailer's factory lighting was non-submersible so I decided that the rain must have seeped into the lights and shorted them. I went out and picked up some new submersible lights for the trailer (replaced the wiring while I was at it) and the same problem still exists: running lights work fine, nothing in the back works.

Now I am thinking maybe the converter in my lighting harness shorted out, but why would the running lights still work? Here's some more information:

Car: 2011 Mazda 3 Hatch
Trailer: Harbor Freight 8x4 utility trailer
New Lights for trailer: Navigator LED lights from Pep Boy Navigator 2 Piece LED Submersible Comb Trailer Lamp Kit - For All Trailers Under 80" Wide | Product Details | Pep Boys
Wiring Harness: Tow Ready Custom Fit harness
Tow Ready Custom Fit Vehicle Wiring for Mazda 3 2011 - 118420

Any ideas?

 

[Rubiconcruiser]

There is a possibility it is a grounding issue after the fact it was a Harbor Freight trailer, There good in some respects but dont ground all that well unless a ground wire is pulled from the battery, check ground first, second double check the connectors. Trailer has Too many connection points on the build to get a good ground established and maintained. All the hardware is bolted and they loosen just a tad your ground potential goes away.

 

[DaytonaJoe]

Hey that's a good point and you just reminded me of another issue. When I first started troubleshooting I realized I had been running the trailer for a couple weeks with the car-side ground just floating around, not attached to anything. It's attached now but the problem is still there. I'm not particularly electrically inclined: what kind of damage could that have caused?

This brings up another question too... the new tail lights have their own grounding wires (the old ones didnt), and I have them mounted out on a 4x4 piece of wood. Could I just ground them to the aluminum bracket that holds them onto the wood? Would it be okay to just use the bolts that come out of the back of the light for that?

 

[cruiserpilot]

I'm a bit confused, but wood is not a ground. In fact aluminum is a crappy ground, so find steel to ground to if you can. Have you ever heard of Dielectric Grease? It is used to keep electrical connections water and contaminant free, i never plug anything outside on my cruiser or trailers without it. Missing a ground won't damage anything,

 

[Rubiconcruiser]

Your case of a missing or floating ground as you call it, The Navy calls it something else, will not damage anything, your electronica are not hi tech and sensitive enough to be involved. Always run the ground to bare metal, and aluminum is fine as long as it is solid, the bare metal allows continued conductivity, Splice the tail grounds together and bond them to the same surface you ground the other equip to.