N16 pulsar electrical issue

[Marto48]

Gday everyone, purchased a n16 pulsar today not running, turns out it was a blown 80a battery fuse. Have replaced, and has blown it again, any idea what I should start looking for? Got a feeling previous owners have jump started it with the wrong polarity. There was a blown 80a fuse, and probably 4-5 other fuses blown for a/c, audio, lights, etc.

[kt53]

If you use Facebook I suggest joining the 'Nissan Pulsar C13 Owners Club'. Most of the people who were members here have migrated to that, and there is little activity here.