12v problem ?

my question refers to a swift supreme globetrotter, year 2005, the problem lies in the 12v system, on leaving the van 2 wks ago all working.
returned yesterday, to find no 12 v , checked all fuses, found 2 spade fuses blown, supplying power to 2 circular roof lights, on replacing these still no power anywhere, these no longer blow, charger working ok ,meter test on battery supply leads.
Removed Norde ellettronica control box, suspect possible relay, but not sure ! removed earth connection ( push in)
this allowed lights and pump to work, initially, on swiching off 4 switch's on box the water pump started, with all taps turned off, ! when attempting to lift sink tap lever, pump immediately stopped and no longer works.

the main 12v switch above door has no effect at all, so somethging is by passing it could this be an earth loop ?

Your comments please