Top tip from Team Muz is to use a polarity tester like this....
....or this....
....where all three lights come on if everything’s in order.
From experience, don’t use one like this....
....where only two come on. If you’re pitching up on a campsite in the dark and are scrabbling about with cables & adaptors, you need to be absolutely certain that you’re plugging your van into a safe supply. It’s really inconvenient to have to examine the legend on the plug to see whether it’s ok, illuminating the area with the light from a mobile phone, and maybe having the plug upside down (note that if the live & neutral are reversed which is the most likely fault, two adjacent lights will be on and if you're holding the whole thing upside down you'll think it's ok). And maybe after a glass of
rioja....
Use one of the top two, three lights on and you don’t have to think, you’re in business
