Not sure but I wonder if dach is the + and dacc is the -. As to the fuse blowing, it is a little weird but I wonder if you've got a dud new board(however unlikely). The fact that it doesn't blow a fuse with the board disconnected, is also weird. Is the loom going to the board from the controller to the top of car? If so I would try to run a 'test' loom(outside of ducts/existing wiring) to prove your not getting some induced voltages in it, or a short that is only apparent when connected to the pcb. Anyway some food for thought.