When we try to start rv it will crank then slowly die down on crank like battery is dead. However, we can use the emergency start and it will fire right up but only if we are plugged in. Does anyone have any idea what the problem could be?
If it starts when shore power / converter are supplementing the batteries, it sounds like battery issues of some type. Make sure the cables are clean and making good contact with the battery terminals - both chassis and house batteries. Charge the batteries, then test voltage with the charger / shore power disconnected for 24 hours.