Alright I'm lost... Jimmy's wiring tested good with a test light.
Sanded down all the grounds to bare metal.

I have:
Tail Lights
Left Turn Signal
Hazards

I do NOT have:
Right turn signal (well, I do, but, when I turn on the right signal, it blinks, but so does the left turn signal, just not as bright. Kinda like it's grounding through the left turn signal)
Brake Lights
Side Markers (interesting here because these are connected to the tail light wire, and the tail lights work)

I have power at plug (trailer end) where everything is supposed to be. I have power on brown wires (tail lights) at the back of the trailer when the tail lights are on. With the brake lights on, I do not have power at the brake light wire, either side, but there is power at the plug still.

What are the chances two different wires (the yellow and the green) have brakes or cuts in them to cause them to short out? But wouldn't that cause the hazards to not work, or the one turn signal that does work? I'm so confused....

 

So you are getting the correct signals at the vehicle plug? Sounds like it is time to rewire the trailer. Would actually be quicker than tracking down the issue. I'm responsible for 34 trailers at work. I have become a pro at rewiring them lol

 

Yes I am getting the correct signals at the vehicle plug.

That sucks, because this WAS my re-wiring, lol. I think I might have gotten a bad harness, but, I'm not sure, because of the last statement I made. i've got 1 correct turn signal, which means yellow wire is good, as is the brown wire... you know what I just thought of something... Maybe My brown wire is the culprit. The tail lights work like they should, HOWEVER, when the brake lights are applied, the brown wire is still getting a signal from the vehicle's plug, but the tail lights go out. It's a dual filament bulb, the tail lights should stay on... Maybe the brown wire is at fault? Actually, that might make sense since the side markers hook into the brown wire, but they aren't working.

I have another brand new harness so I guess I'll be swapping that out for the one I just put in... heh, another 2 hours wiring it all up here we come.

 

What did you follow in terms of a wiring diagram? What are you working on? What wires were present at the back of your truck?

 

I have the standard 4 pin harness on the Jimmy.

The tail lights are self grounding lights on the trailer.

The white wire is grounded to the trailer frame.
The yellow and brown wires are hooked up to the driver's side.
The green and brown wires are hooked up to the passenger side.
The side markers are hooked up to the brown wires.
The grounds are sanded down to bare metal.

The trailer is a little 4x8 like the ones sold at tractor supply or harbor freight.

This is the exact diagram I followed. The only thing I can think of is a bad light, or bad wires or something. I could use a 9v battery to test the individual wires on the trailer. That should be enough to light up the bulbs.

 

So you re-wired the trailer and now are having problems.?

What's odd is that the hazards work, but the brake lights do not. For brake lights, both the yellow and green wires are powered. For hazards, both the yellow and green wires are pulsed on and off...

Do your tail lights have dual filaments? Did you wire the brown wire in properly to the lower wattage filament?

 

Yes. Bought the trailer for $50 with no lights on it at all. No harness, no lights, only thing left was the brackets for the lights. The guy got a new trailer and needed the light kit for his new one.

THIS RIGHT HERE is what I don't get. Only thing I can't think of now, is I got a faulty kit or something. Like you said, the hazards and turn signals use the same wires as the brake lights. So why do the hazards work and not the brake lights when the vehicle wiring is sending out the proper signal.

Yes they have dual filaments. The brown wire is in contact with the lower wattage filament.

 

Good news! I fixed it today.
Turned out it WAS a ground problem. I sat down today, watching the turn signals flash, and realized, they were grounding through the bulb on the other side. All of m grounds are down to bare metal, but I guess since this trailer is a tilt/folding trailer, somewhere between where it folds there is a bad connection.

Someone told me to try hooking up a jumper wire from the a frame before the tilt mechanism, to the trailer frame after the tilt mechanism. After I did that, my side markers started working, which clued me into the ground issue. After that I ended up running each rear light, it's own ground wire, up to the side marker grounds, and bam, everything worked perfectly.

Really BIG thank you to all you guys for the help.

 

Glad you got it working. Faulty grounds can be a PITA.