I bet this will stump you too (electrical problem)

we all know that trailer lights (the standard ones) are junk. so when the running light function on my drivers side trailer light went out, and a new bulb didn't fix it, i jsut replaced the entire light.....well, it still doesn't work.

here's what i've come up with.

-it's not the bulb: tried new bulb and entire new light

-it's getting power: volt meter read just under 12volts at the tip of the wire that splices into the light itsself.

-i don't believe it's the ground: the turn signal and brake still work, and as far as i know, they share a ground with the running lights. so if one goes because of a bad ground, the other does too correct??

-it's not the housing: i took the passenger side light (that works) and hooked it up tot the drivers, and it didn't work.

-i'll also not that it has side markers tied into the running light circut, and both sides work for those.


so the only thing i can think of is that i am wrong, and the brake/turn signal does not share a ground with the running lights inside the light housing.

I'm pretty good with wiring and lights, but this one has got my scratching my head.

I'm pulling the trailer about 4 hours later today, but i should be at my destination before it gets dark, so i have time to fix it, but if anyone can think os something i missed, that would be awesome. i'd rather not rewire the entire trailer.....

 

Holy crap man. How is that happening?? I looked at my trailer and they appear to share the same ground on mine. I am assuming you are using a 4 pin and not one with brakes or additional pins.

Instead of wiring could you cheat a wire over from your working running light on the other side with a Scotch tap for the time being? I'd be curious to know if that works.

 

its got to be the ground. Splice in a ground wire right before the bulb and touch it to the frame. It should work.

 

yep, 4 pin. it's just a small off road trailer, so no need for brakes or anything fancy.

and i could splice fromthe other one, but power isn't the issue. i'm getting the full 12 volts from the lead for the running lights.

that's probably what will end up happening, i'm just stumped as to why....
i made sure to scrape off all paint around the nut and bot contact points on the bracket, and i welded the bracket directly to the frame. it just stunps me how it isn't getting a ground from that. i'll got cut a piece of wire and try grounding it manually on my lunch break.

the fact that the turn signal and brake light still work on that side is what's really throwing me off. i'd considder that maybe it couldn't draw enough current to lihgt it up after already powering the side light, but they aren't LED, so you'd think at 12 volts and even a little bit of power, thebulb would at least be dim.

 

What are you using to test for power? A multimeter pulls almost no amps and will show voltage present even when the wiring can't deliver enough amps to light your bulb. A test light is a better choice.

You can also leave the bulb in the socket while using a multimeter to test for voltage. If you have a marginal splice connection somewhere, you will see voltage with the bulb removed, but it will drop out with a load on it.