I am having trouble with the interior lights. With the trailer hooked up to shore power, the lighting is dim unless the batteries are hooked up and charged. I do have 110vac at all outlets, and going into power converter. I confirmed 13.6vdc leaving the converter. All fuses are good, and show 13.6vdc. The entire 12v circuit seems to not have enough power while plugged into shore power with batteries disconnected. It is only when the batteries are reconnected that I have enough power and lighting is bright. Also the batteries do charge when plugged into shore power. Any suggestions would be greatly appreciated.