1970 GTO lighting problem.
 

I have a scratcher.
My GTO has lost it's parking lamps, dash/interior lighting only.
brakes,turn and hazards work perfect. all grounds new and switches new (quality as i could get).
after testing at headlamp switch;
OFF - red and brown/wht wire 12v
Park select- red 12v, brown/wht open. no power any other pin.
On - red 12v, brown/wht open , lt blue 12v , no power to other pins.
fuse good 12v
inst lamp fuse no power in or out.
what could cause this?

Never mind , figured out. fuse , wasn't burnt. has a hairline crack in it , that opened when under load. never saw anything like it.