hey guys i have a 10' trailer i use to pull my four wheeler and i noticed last night that the left side lights are out which is the brake light, red marker light, and an amber marker light. i checks the three bulbs and they are all still good. i checked the wiring and it all looks good. the grounds look to still be good.

anyone know what could be causing this? any help would be great.

 

Are there any junctions or is the 4 prong damaged. You may need to trace the wires from the front to the back with voltage to it and a meter. Check for any breaks or anything going on at any junctions.

 

If the right side amber works, you have a damaged wire after the split in the wires for the amber lights, same for the tail. If one tail works and the other does not (assuming the bulbs work swap bulbs side to side). It is not the truck end. brake is a totally different signal wire (right and left) but I'll bet you will find both brake and tail/marker wires broken or otherwise damaged.