I just love trailer light electrics.....Nothing makes any sense.....EVER..... :crazy: :crazy:

Most likely bad ground.

On some vehicles the brake wire is grounded when not lit. Here's what happens case where you have a bad ground. 12 volts is on one side of the running light element in the bulb, there is no ground on the ground side of running light element (bad ground). The ground side of the running light element and the ground side of the brake light element are tied together in light fixture. Since the hot side of the brake element is grounded when not in use, ground is going through the brake element to ground the running light element. Both elements of the bulb are usually lit when the lights are on.

Remember that the ground is being supplied from the hot side of the brake element, well when the brake pedal is pushed, it removes the ground and put 12 volts on the brake element like it should, but now there isn't a ground for either element and all the lights go out.

Since there is no ground, I would be getting in the boat.:D

here is your source for the blinker fluid

http://www.kalecoauto.com/

:D :D

I would start over. I would tie the new wire to the old and pull it through so you can start over. It is a ground, the best way to know is the lights going out with the brakes on. There is no way of chasing down the problem without either making it worse, make a small problem that does not show yet worse, chasing problems like this can be endless unless you start over. In short, I would start over.:D Plus you are in salt and a wire could be bad in the middle from salt wicking up the wire and breaking the current. Now that I see where you are from there is no choice but to start over.

A new set of "LED" lights, and I'll be "starting over".

Yes those LEDs are cool. Go to an underground sprinkling company and get the grease boots they use to connect wires for underground use, they are packed with die electric grease and will never crowd. I have a snowmobile trailer and I used these to replace the lame clips they used. Salt and copper means green dust over time, a short time.

outlaw sed "My trailer does not grounds through the trailer hitch, it grounds through the plugs"

That's what I'm trying to prove, whether the plug ground is good.

Thanks for the suggestion, that is a strong starting point.

It is a bad ground.

If you have narrowed it down to the tail markers, that wire color is brown unless altered. test it with the truck and trailer connected at the tongue then test at the lights this will give you an idea of a brak or not in the system if the test light dosent light up at the lights. Also check the truck plug first before you continue to the trailer.