Several times I've just looked at a fuse and said OK.  Then find out
later that the fuse link has broken, etc. Auto electrical is a very
mysterious, sneaky business.  :-D

Once I had a 6-month old car blow a fuse when stepped on brake.  It took
me a week of no brake lights to find the cable was pinched under an
external star washer and it took 6-months to finally cut through to the
brake lite wire.  I finally remembered a trick I'd seen a pro do once in
a pinch: Replace the fuse with one covered with cigarette "tin foil" and
 let 'er smoke.  Did the trick!

I don't necessarily recommend that!