One of my brake lights on the trailer is not working. Running lights work and turn signals work, just one brake light not on. Any ideas? Thank You.

Bulb or ground most likely. Make sure you have a good ground. 

Check the bulb first, mine blow constantly. Helps to unhook lights when putting them in the water

There might be a problem with the module on your car/truck.  A lot of new cars and trucks use a pulsating digital signal to control the LED lights of your vehicle.  So they're not directly compatible with bulbs in most trailers.  So you need a specialized control module to convert that pulsating digital signal to a steady DC signal that will operate the bulbs.  

 

The reason I say this is usually the same signal is sent for brake lights and turn lights.  So if the turn light works, but the break light doesn't, that says to me that the wiring and bulbs on the trailer are likely fine.  However, as noted, it could also be a ground issue, as there might not be a strong enough ground connection to run both brake lights at once, but still a strong enough ground to run just the one at a time.  

More then likely a bad bulb. Some trailers use bayonet style bulbs other you replace the entire sealed module.

Tom

 

If you're not using LED lights, make the change! If you blowing bulbs and don't want to go to LED lights, go to the auto parts or hardware store and buy some die electrical grease. Remove your bulbs and smear a film of the grease on the bottom and the base of each bulb. I even put on the connection between the truck and trailer. Do it at least annually and your problem will be solved. That's assuming it's not a ground issue. Even if it is a ground issue, die electrical grease is cheap and it works. I even put it on the base of all of our exterior and patio bulbs.

3 minutes ago, volzfan59 said:

If you're not using LED lights, make the change! If you blowing bulbs and don't want to go to LED lights, go to the auto parts or hardware store and buy some die electrical grease. Remove your bulbs and smear a film of the grease on the bottom and the base of each bulb. I even put on the connection between the truck and trailer. Do it at least annually and your problem will be solved. That's assuming it's not a ground issue. Even if it is a ground issue, die electrical grease is cheap and it works. I even put it on the base of all of our exterior and patio bulbs.

I been blowing them even smothered in the grease. I even had a bulb full of water the other day. I’ve got LED on one side and not the other, might be the problem haha. $50 is a rough pill to swallow for something you dunk into a river full of rocks and logs . 

Switch the system over to LED's.  Very trouble free long term.  You will not regret it.  You will still need a good ground, but once you have that and the system properly wired, you'll have no more light troubles for years.

26 minutes ago, TnRiver46 said:

I been blowing them even smothered in the grease. I even had a bulb full of water the other day. I’ve got LED on one side and not the other, might be the problem haha. $50 is a rough pill to swallow for something you dunk into a river full of rocks and logs . 

As a fellow river angler myself I can probably bet you lose more than $50 worth of baits in a season to

One thing to remember too is that LEDs can handle vibration and impact very well and also will never need to be replaced.  I just replaced my trailer lights with LEDs after trying to chase down a faulty connection somewhere.  Well worth the afternoon of rewiring and $50.

Sorry, forgot to mention that I do have LED lights on the trailer, so will look at the ground wire first and go from there. Thanks all.

19 minutes ago, flyfisher said:

As a fellow river angler myself I can probably bet you lose more than $50 worth of baits in a season to

One thing to remember too is that LEDs can handle vibration and impact very well and also will never need to be replaced.  I just replaced my trailer lights with LEDs after trying to chase down a faulty connection somewhere.  Well worth the afternoon of rewiring and $50.

Til you back into a log underwater with your $50 lights haha. Just replaced the “never needs replaced” LED with incandescent 

15 minutes ago, rboat said:

Sorry, forgot to mention that I do have LED lights on the trailer, so will look at the ground wire first and go from there. Thanks all.

On the LED, the wires are soldered into a cutting board type thing. I’ve had them come out too, only takes a Phillips screwdriver to at least check 

2 hours ago, TnRiver46 said:

$50 is a rough pill to swallow for something you dunk into a river full of rocks and logs . 

The set I have now was around $39.00 at Harbor Freight. That was pre economic downturn/ inflation so they're probably more expensive now.

15 minutes ago, volzfan59 said:

The set I have now was around $39.00 at Harbor Freight. That was pre economic downturn/ inflation so they're probably more expensive now.

Still affordable through Amazon - these are the ones I put on the F-9 trailer. I paid $21 last year...they've gone up to $27 now for the whole kit.

https://www.amazon.com/dp/B008CE0W5Y/ref=emc_b_5_t

25 minutes ago, volzfan59 said:

The set I have now was around $39.00 at Harbor Freight. That was pre economic downturn/ inflation so they're probably more expensive now.

I’ll check! 

1 hour ago, TnRiver46 said:

I’ll check! 

I think i got mine from Harbor freight as well when I did mine.

9 minutes ago, flyfisher said:

I think i got mine from Harbor freight as well when I did mine.

My new experiment is old school lights and unplug every time you launch but I still have 1.5 working LEDs haha

I put all new LED trailer lights and wiring on my trailer two years ago. I still unplug my lights before I put the boat in. I plug them up when the boat comes out and check them before I leave. I got mine at Academy. I think the whole kit was around $50.00.

Trailer lights only work in the driveway!

 

Soon as that cop pulls up behind you one will quit working.

Just to finish this one, it turned out to be a bad converter control module box that hooks into the lights on the truck. I was a bit unsure about the repair so I had it rewired at my local U-Haul place. Thanks everyone!