trailer lights not working

[Uturn]

2018 Subaru Forester
used trailer with new LED lights

The Forester has a factory plug for trailer lights, I installed a 4 pole kit that plugs into the factory plug.  Test light shows brown has power with brake and running lights.  Yellow and green work as intended.  These tests were done at the plug without the trailer.

Plugged in the trailer and have no trailer lights, no running, no turn, no brake.  I tested brown at plug to brown at light, yellow at plug to yellow at light, green to green, and white to white.  All showed zero ohm. 

I did not test volts at the lights because I had to disconnect the trailer to go get multi-meter batteries and didn't feel like hooking it back up and my test light isn't long enough.  Any ideas why I don't have lights? 

[Uturn]

9v battery directly at the light lights them up.  I guess I'm chasing a ground fault.  (sigh)

[hacem]

You should consult an electrician on cars.

[ChpBstrd]

A dog or squirrel may have chewed the wires. You could trace the wires and look for the break and then wire nut it, or just buy a new harness off of eBay.

[PlainsWalker]

Strong pass on using a wire nut on a trailer. Trailers rattle, shimmy, and shake so much that I've had nuts back off. I've started using crimp connectors instead.

I agree on something shorted. Trailers tend to be made so cheaply that more often than not the factory wiring is run with no looming. So critters or just a wire rubbing its insulation off on some bit of metal.

[Car Jack]

Make sure the ground goes to the ground WIRE.  I've seen clowns at UHaul wire trailers just relying on the ball to conduct the ground.  They won't.  Make it all wire on the trailer if they rely on the frame for ground.  Also, without a "converter box", a Subaru won't give you directionals.  American cars will blink the brake light.  Subarus blink a separate amber light.  I've added a connector and a couple amber lights for directionals on my trailer and it works great.

[Uturn]

It was a new light kit, so no critter chewing. 

I don't know where the problem was, but pulling my connections apart to test and reconnecting fixed it.

[WSUCoug1994]

It is more than likely a ground issue - I am sure your car grounding is fine.  It likely has to do with the trailer ground.  Even if you wired it wrong to the plug you should get some light activity on the trailer.