Check fuses in the box under the hood by opening the case, removing each fuse, and inspecting the fuse for signs of breakage. The exact process varies by vehicle make, model and year, but most vehicles follow a version of this process.
Mechanics who know which system needs a fuse checked can use a diagram included in the owner's manual for each vehicle that shows where the fuse lies in the box under the hood. A copy of the diagram may also appear under the case lid. Otherwise, users can check each fuse individually by opening the cover and visibly inspecting each in sequence. Many cases have latches that prevent accidental disconnects. Remove these to access the series of fuses underneath.
Pull out each fuse in sequence, or remove the fuse desired, and visually inspect it for signs that it no longer provides a true connection. A fuse that burns out separates in the middle and prevents further electrical transmission through the circuit. Blade and glass fuses typically have clear centers that allow vehicle owners to confirm the state of the fuse at a glance. If the wire in the fuse no longer connects on all sides, replace the fuse to restore electricity to the related system.