Had a 500l twin operator van system fitted a week last tuesday, Used it on the wednesday and now its fooked

. Had a few cold nights the other day but had an oil filled radiator on low all night to prevent any problems. Came to turn on the flowmasters yesterday and the fuse blew, Changed the fuse and now instead of flashing BAT on the flowmasters they have gone tits up, Not charging when the van is running and when switched on just broken letters showing on the display.
Can anyone help me with advice on how to sort it out, P*SSED off is an understatement as like i said only used it for bout 6 hours so far and it set me back £3300

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