All good info posted here, Ok a quick way to check the converter, dis connect the - negative battery cable the one attached to the trailer frame. plug into a 110 volt power supply, are the 12 volt lights on, normal brightness? If they are converter is producing 12 volt power, now connect battery neg cable, using a VOM ( volt ohm meter) check voltage across the battery, should be around 13.5 volts, if yes all is good. If no check fuses or get into Herks troubleshooting guide! Good luck.