Open the hood of the car and up near the windshield on the right side, looking from the front to the back, is a black fuse box that clips shut on the front. Lift up the cover to the box and attached to the inside of the cover is the fuse diagram.
Answering "Where can you find an online diagram of the underhood fuse box on a 1999 Honda civic ex?"
1999 mercury tracer fuse panel diagram
The fuse panel diagram is found on the back of the cover of the fuse box. It is also found in the maintenance manual.
fuse box cover
Owner's manual, or Library.
the owners manual
You can find a 1999 Chevy Tahoe engine fuse block wiring diagram in the car's owner's manual. You can also find it at most auto part stores.
autozone.com has alot of helpful info
where can i find a fuse panel diagram for a 1999 vw beetle
You would find that information in the drivers manual.
The 1999 Pathfinder fuse box diagram can be found on the inside cover of the fuse box. The diagram can also be found in the owners manual.
It should be on the back of that little compartment which covers the fuse box.