Its reversed polarity this means the live brown wire has been connected to the NEUTRAL TERMINAL(N)
and the blue neutral wire has been connected to the LIVE TERMINAL (L).
JUST CHANGE BACK TO BROWN (L) BLUE TO (N).
go to www.caravanclub.co.uk click on 'Ask a question' top of the page. when next page shows click the first one 'How do I solve reversed polarity then click on the 'reverses polarity PDF it tells you all you need to know.
Bob
December 2010