RV Repair: Inverter, fuse panel, trickle charge

Question
I just bought a 2001 Fleetwood Mallard in excellant condition. My question is when plugged into 120 volt 15 amp and the battery disconnected the only things that work are the 120 receptacle plugs. No 12 volt lights or anything else. Does this mean the inverter is not stepping down to 12vdc side, or does the battery have to be hooked up.But the battery doesn't seem to get any trickle charge from the 120. Fridge won't work even on gas if battery is disconnected and 120 is attached. But works on gas when 120 unhooked and battery attached. Please advise me. Thanks

Answer
Brian, First is you are describing what a converter does. The difference is a converter converts 120 vac to 12 volt dc. An inverter turns 12 volt dc to 120 vac. When you are plugged into and power you should have power to the 12 volt. If you don't check the converter to see if it is putting it out. If not verify that the plug it is in has 120 vac. If so the converter is bad and needs replaced. If there is power coming from it make sure it is at least 12 volts and then go to the batteries. There you should find circuit breakers for the 12 volt. They look different but they will have 2 wires connected to them. Sometimes even more. But check there to see that power is going to both sides of the breakers and if one isn't replace it. If your batteries are charged up does everything work inside? If not then it is probably a circuit breaker or the fuse panel. Let me know what you find out, Bill