I dont have a Jayco, but first thing to check is what do you have... When plugged into 110 volts you are getting 12 volts to work your lights, that proves your converter is working. When not connected to 110 volts == nothing == so that means your battery is not giving its 12 volts ... first and easiest is to check ALL fuses. Sometimes fuses work loose, and while they are not blown, they dont make contact in the holder. Next is the Battery connection. A small volt meter is the easiest. A jayco owner will help you on specifics.... welcome to the best Camper site on the net.