Never put your trailer on the road with questionable wiring or a lighting system that is already known to be failing. As drivers slow down behind a vehicle that is pulling a trailer, they will often instinctively focus on the bright brake lights as a reference point for where to stop and how quickly the vehicle in front is stopping. If you've got bright, well functioning brake lights on the trailer, these lights will catch the attention of the drivers behind you, regardless of how much they are paying attention. If your trailer's lights are dim or nonexistent, those drivers will focus on the lights on your vehicle, which likely will not give them enough time to stop, which could result in an accident. While they might be deemed at fault, no one needs the headache of dealing with insurance companies—nor do you want whatever cargo you are carrying to be damaged or anyone to be injured.