Hello, both the trailer driver and passenger brake lights are lit when the lights are on. I assume those are the running lights. When the brake is applied, the driver light gets brighter but the passenger light stays the same. I believe the passenger side brake bulb needs replacing.
From the looks of it, the round light cover pulls out, but before I do that , does anyone know how to access the bulb in the Brenderup brake light? Thanks.
It’s not unusual for the bulb to be a two-element bulb; one is lit for normal brightness and the second element is lit for brakes/turns. So don’t be surprised if there is one bulb in there.
I unfortunately cannot help you with the key piece of your question as I don’t know what kind of lamps are on the trailer. If you can remove the round light cover, the bulb may be directly accessible from there. Once you do get to it, there should be a number on the bulb that you can use to cross reference a replacement.
http://www.mountaintoptrailers.com/brenderup-trailer-parts.html
These guys may be able to help, if all else fails.
Hubby says the light fixture is a sealed unit, and the wiring for the unit as a whole looks great, and therefore the problem must be with the tow vehicle’s wiring harness. (Does that make sense? Other lights work fine; just not that side.) Will have to deal with getting tow vehicle to someone who knows what to do with a trailer wiring harness, which seems to be quite a challenge. 
Thanks for the suggestions. The light appears to be a 1 piece unit held in with a rubber grommet (pry out the light with a flat head screwdriver or similar object). I need to do some further investigating to see if it is a wiring issue or a faulty light unit. Thanks again.
[QUOTE=SharonA;7923655]
Hubby says the light fixture is a sealed unit, and the wiring for the unit as a whole looks great, and therefore the problem must be with the tow vehicle’s wiring harness. (Does that make sense? Other lights work fine; just not that side.) Will have to deal with getting tow vehicle to someone who knows what to do with a trailer wiring harness, which seems to be quite a challenge. :-)[/QUOTE]
Possible, but easily checked…just plug into someone else’s trailer that also uses the four pin connection like the B’rup. It can be a simple utility trailer for that exercise…doesn’t have to be a horse trailer.
I do not think it is a wiring issue (but I could be wrong). I think the passenger light unit is defective.
I tested out the lights this morning with my other car, and this time the passenger unit running light did not work, but the stop and turn worked. Yesterday, on my other car (which is new and the first time I hooked it up to the trailer), the passenger unit running light worked, but the stop did not (I forgot to test the turn yesterday).
Anyway, I popped out both lights from their rubber grommets using a large flat head screwdriver. I switched the lights so the passenger light was now plugged into the driver side, and the driver light was plugged into the passenger side. The allegedly defective unit exhibited the same results on the driver side – the running light did not work, but the stop and turn did. The good unit now on the passenger side fully worked for run, stop and turn. Given that, I believe there is a short in the defective unit (I can see water inside the unit which is probably causing the short), so I am going to buy 2 new matching LED units (trailer is 10 years old) and see if that corrects the problem.
As an aside, it’s possible that my new car is not wired the same as my old car, and I may need to get that fixed.
Regarding the 4 pin connection mentioned above, this Brenderup has a 6 pin round, which I converted using an adaptor to a 7 pin flat. That conversion worked perfectly on my existing car. The new car came with a built-in 7 pin flat, so at least I have the same connection on both cars. I just might need to rearrange the wiring on the pins in the new car’s 7 pin flat.
For those looking to replace their Brenderup rear run, stop and turn light units, the cutout hole in the Brenderup is 4.5 inches, which is a common size for a trailer, and takes a “standard” rubber grommet into which a 4 inch round light unit fits. The units are sealed, and the bulbs cannot be replaced. The units have what appears to be a “standard” 3-prong connection, so the new lights can be installed by plugging the 3-prong connector into the new light unit, without splicing wires. The unit is popped out of the grommet with a flat head screwdriver, and is installed into the grommet by pushing the light into the grommet.
It does sound like you have an issue with the light unit…the water isn’t a good sign. I actually just ordered new rear LED lights for my utility trailer because one side just will not function reliably and the wiring all checks out fine.
Weird that your trailer hookup had a six pin…4-pin is standard for a trailer without electric brakes and 7-pin with brakes. These days, at least. At least there are adapters available!
So it turns out the unit is shorting, likely do to the water inside the unit. Today, the unit worked perfectly on both cars, which likely means the water dried somewhere inside the unit. To avoid this issue in the future, I am going to order up some new LED light units. Thanks for all your help.
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