Hi iv reciently bought a 1995 transit hereld witch has an atwood confonfort 3 warter heater and blow air heating i was wondering how this atchally works as iv neaver had one of these before does it need to have warter in it before i use the heating as it looks like a warter boiler iv had it enighted but quickly switched it off as wasnt sure about how to go about useing it if any one has any idears that would be grate thankyou