from a previous post on slide outs
Hi, I have a 2006 Newmar Kountry Star, (gasser)
you have an automatic transfer switch
converter gets power from which ever 120v source is the being used
shore or generator makes no difference
how long does 12v power last after you turn off the engine
are those the original 9yr old batteries
if those batteries are bad, you may have blown some fuse on the converter
i think you need to call a mobile RV tech or take it to an RV shop
you know nothing about how anything electric in the RV is attached or works
it will be safer for you and the RV to have somebody else check things out