i agree with what nash said on cking the batts and such ,, but one other thing ,, if u switch the battery switch to "store " u will not have any 12 volt power ,, even though u should when plugged in ,, the store thingy is only when u are gonna store it ,, and it will not let the batts run down due to draws in the system , but one thing that u said kinda bothers me ,, and that is the fact that u said " the lights go out when plugged in" ,, this should not be ,, the converter will run all 12v and 120v stuff when plugged in ,, even if the disconnect is off ,, it will not charge the batts ,, but other stuff "should work " i hate to be a buzz killer ,, but the way i take it ,, is that ur converter is going bad ,, or is bad ,, not for sure ,, JMO ,, but sure looks that way,, but one other thing ,, how old are the batts ,, and have u cked them with a hydrometer (that is the best way to ck batt status ,, imo ) ,, but u should still have power when plugged in ,, the converter will provide that