Screwy Trailor lights

Alright I just put new lights on a spartain boat trailor.Kids broke others thought it was a jungle jim.My left/right signals and brake lights work,running lights work.Now with the running lights on both signals will work but as soon as I touch the brake all lights go off,once I let off the brake the running lights go back on.It only happens when the running lights are on.
I’ve tried differnt wire,diff. grounds but nothing.These new lights have ground wires coming out of them also,but I’ve left them off,put one then both on and nothing seems to change .Any help will be greatly appreciated,I’m not sure I know what I’m doing .

Sounds like you have a ground problem, or lack thereof. The ground circuit seems to be able to provide ample service for the lower wattage running lights but cannot support the additional load created by the brake light elements.

I bet they act real funky if the running lights are on and then you turn the flashers on too.

Usually this is a result of a weak to no ground from the trailer to the tow vehicle. Some wire harness use a dedicated wire that grounds within the harness on the vehicle. My personal favorite way to ground the trailer is to use the ground terminal in the trailer plug and have the vehicle side run directly to a clean, protected ground in the vehicles interior behind a trim panel.

On the trailer side of the connector run the ground to a clean, protected area of the frame. Use marine grade connectors to attach to the frame (has to be unpainted section of frame) and then seal it using liquid electrical tape.

Good luck!

oh yea, definitely a ground problem

Great Info Riveratt

Riverrat that is the thing I didn’t understand,it all works fine like it should until I turn the running lights on and then hit the brakes,the signals work fine with the running lights on.It is like the brakes are the off switch,when I press it down they go off when I let off the brake everthing comes back on.If I do the same thing with out the running lights on they do what they should even w/ the singals on.Its done the same thing on two trucks.I’ll switch the ground like you said.Thanks.

Use your battery charger to supply 12volts to each lead of your trailer connector and see if your lights work that way. Also take a meter or test light and check the output from your vehicle connector to see if the same drop out occurs. Sure sounds like a ground issue to me.

Their draining enough current through the brake wire to make up for a bad ground. 99% sure on this one.

If I’m wrong, I’ll drink (gasp) a beer (will also do this if right).

Thanks for the help guys,going to work on it tommorow.

Definitely sounds like a ground problem. What you may see is that all of a sudden everything starts working for awhile. As the connection between ball and hitch gets better (grit and scum works off) it may start working. A quick way to check and see if that is the problem it to spray the ball with WD-40 and then put the trailer on and check the lights, if it all works it is definitely a ground problem.