Peculiar trailer lighting issue

[yonipainting]

So, all of a sudden I lost my trailer lights one day (lost power to them) Brake lights work, turning signals work. Same symptoms behind both of my tracks.
I tried to chase the problem today. Didn't find anything but ended up completely re-wiring the trailer. Symptoms stayed the same.
This is what I noticed : With trailer disconnected,from the vehicle, there is power on the light connector (vehicle side). As soon as I plug the trailer in I loose that power (ON THE VEHICLE SIDE ??? - no fuses blown). I disconnect the trailer plug, turn the lights off and on again - same story.
I then disconnected the ground on the trailer side. With ground disconnected, i plugged the trailer in - power stayed. As soon as I touch the ground wire to the trailer - power goes off !!!
That was the point that i figured this problem was above my pay grade
Maybe I should mention that I have LED lights on the trailer and don't know much about them. Everything was running fine since the beginning of this season.

 

[yonipainting]

Cmon, I need an expert here

 

[Grandad]

When weird things happen, usually it involves grounding. I'd start by running a piece of wire loosely lying beside my vehicle connected to a clean negative battery post and a known continuous piece of trailer frame or even directly back to a negative connection of the light fixtures. If you don't have a spool of wire or are cheap like me, perhaps you can even use an extension cord, but the connections must be something you can rely upon. Then see how things operate. If you still have trouble, at least you can be assured that the ground will not mess up your test results.

Another thing is that a meter, particularly a digital meter, and also LED lights used as test lights can easily fool you as they can react to very low currents that really don't prove that you have a patent circuit. - Grandad

 

[kmarine]

I agree Try running a jumper cable from truck frame to trailer frame and see if this fixes the problem

 

[fishin98]

It all starts with have a good ground from the tow vehicle to the trailer. Are you using a adaptor to plug into the vehicle light system or did you patch/splice into the wiring? Sounds like you have a short somewhere.

 

[airshot]

Sounds like old wiring that needs to be updated. Time to just start over and get a trailer light kit with all the wires. The one I bought is a plug and play including side lights. All LED lights and spent less than an hour installing new and tearing out old. Now everything works perfect.

 

[naturelover]

Sounds like your ground wire is rubbed against a power wire somewhere.

 

[Silvertip]

Sounds like your ground wire is rubbed against a power wire somewhere.

If that were the case the OP would be looking for fuses. Power to ground = a short circuit and blown fuses.

 

[wahlejim]

Do you have a 4 pin or 7 pin? If it is a 7 pin, pop the cover off and inspect the wires/clean corrosion.