Hi , you have got off to a good start by thanking people for taking time to reply to your post, a lot of people don't do that, thank you too, your fridge will be three way, that means it will run on Gas 12v and Mains when hooked up, when you switch to 12v power the Fridge will only run when the Engine is running as this prevents your Batteries from draining as the Fridge draws about 6 amps when on 12 v, this facility is really only meant to keep the fridge cold when driving, when you reach your destination ,switch to mains power if 0n electric or Gas if not.