I have a caravan the following is based on that,with exception it ain't got an engine.
Take out the light bulb/tube check the rating 12 or 230/40 volt. you will know then. If un-sure do same for other lights. Usually only two are mains as when on site hooked up the 12volt battery should be trickle charged by an on board built in charger.
The following should be or in my c/van they are.
Toilet flush 12volt
Fridge 3way : 12v 230/40 mains.... and gas
Water heater Mains imersion or gas only.
and of course 12 volt lighting with mains also you'll have to check each bulb/ tube to see what's what.
Hope this helps.
bob
June 2009