I have LED lights on the trailer and they always worked well. Today I noticed that the light on the right side looking from the back does not come on when the brakes are applied. The turn signal works on that side and the light on that side works at night, it just does not come on when the brakes are applied. Anyone have an idea where to start. Thanks. 

Since the turn signal and brake light are the same light and work from the same wire, if what you are saying is true then the problem must be in the vehicle's electrical system.

 

Be absolutely certain that the brake light is NOT working and the turn signal light IS working.

 

There are nice testers that plug into the trailer wiring terminal on the car, but I'm not sure they differentiate between the turn signal and the brake light.  

 

Bad grounds are often the problem with trailer lighting, so make sure grounds are perfect, terminals clean.  

 

If an expert finds my facts or logic in error, please explain in detail.   

 

https://www.etrailer.com/question-161374.html

Trailer lights are the bane of my existence 

Try spraying DeOxit into the vehicle and trailer connector before changing out the sealed light unit.

Tom

Wire brush and contact cleaner on the pin connections

I had the same issue.  Mine turned out to be the plug between my truck and boat.  I bought a new one problem solved. 

Two words.

 

Dielectric grease.

On 11/14/2019 at 6:52 PM, Fishing Rhino said:

Two words.

 

Dielectric grease.

That stuff helps 

Solved. Took off all ground wires on trailer, grinded down to bare shiny metal, a thin coat of dielectric grease, reattched all grounds and presto. Works wonders. Thanks for all the help.