Trailer lights

I have an issue with the trailer brake lights.

With no lights on the truck, everything works fine on the trailer. With the truck lights on, when you hit the brakes the trailer tail lights go out (All the running lights are broken). The turn signals on the trailer and the turn signals on the truck blink opposite whether the lights are on or off.

Ideas

Fix your ground on trailer. Then ground trailer to truck.

You have a bad ground connection on one of your lights or on the trailer itself.

Yup, anytime trailer lights go fruity it is usually a ground problem. Make sure the ground pin on the connector shows a good ground to the vehicle frame.

The responders are correct..you have poor or no ground. Hook up and take a jumper cable from the truck to the trailer,make sure each end is on clean metal,then check your lights for function. If you have good ground with the jumper cable you solved your problem..now to fix it. I always run a piece of wire from the trailerframe to the tongue of the trailer,crimp an end on it and metal screw each end on a spot I cleared by touching the grinder to it. This will give you good ground for those lights grounded directly to the trailer frame. Also clean the ball on your hitch and the trailer tongue coupler as ground often goes through that route. By essence your ground should be in the trailer wire harness to the truck wire harness,that doesn't mean the lights are grounding back through to the truck like they are supposed to,they may be getting power as per they are wired but they are not grounding back through the trailer frame. I always run a short wire from the light to the frame,to be sure I have a good ground. I used to do 21 trailers for a friend's business,serviced bearings,springs ,shackles and e-brakes and lights..and like the other responders 99% of the time that a light or e-brake isn't working is because of a poor ground for that appliance

Grounding problem for years. Ran a whole new wire with a ground wire in it two each light and brake. fixed once and for all.

I just wired my gooseneck with the new LED lights. I bought a kit on ebay that came with a weld on bracket, taillite and clearance light. I was impressed!

I agree, bad ground as other said. Except (maybe) for the turn signals.
Once you fix the ground if the the turn signals still flash opposite,
the green and yellow wires are reversed.
I used to wire my trailers and trucks that way on purpose to
discourage people from "borrowing" them. They got tickets.

When is the last time you changed your plugs, both truck and trailer? It could very well be a ground problem and the best place to start looking for that is at the plug. If you live in the salt belt a plug doesn't usually last more than a year for either the trailer or truck end. If the connections are showing corrosion just replace them both, don't try to clean them except for short term because it will continue to be a problem.

We had grounding problems on 2 of our tilt bed trailers. The ground path is through the tilt brackets, and if not used regularly, can get a rust film. We installed a jumper wire around the tilt joint to eliminate the problem. My opinion is that the trailer manufacturers should have already done that.

And those little connectors they use to splice wires together, the ones that you put the wires in and snap the lid shut and it penetrates the to wires to make a connection should be outlawed. They corrode and cause problems in the wiring.

I wired a ground wire from my tailites to the ground in my truck plug on my flatbed. I have had no problem since.

I had to do the same thing on my trailer. The lights drove me nuts for a couple of years till I figured it out.

i run a ground to the frame and every light on my trailers