Hi we have a N reg case 5150. It has recently had a new alternator and the battery is fully charged. It was used all afternoon power washing. Came to move it at the end of the day and switched the lights on at which point it cut out. There is now no power when the key is turned I have checked all the small fuses which are ok. Could it be one of the big main fuses or a relay that is the issue. Any suggestions welcome.