* A broken filament: The thin wire inside the fuse will be broken or visibly separated. This is the most obvious sign.
* A blackened or discolored fuse: The fuse body might be darkened, charred, or melted. This indicates excessive heat due to a short circuit.
* Using a fuse tester (most reliable): While visual inspection is often sufficient, a fuse tester provides the most accurate confirmation. This small, inexpensive tool will indicate whether the fuse is blown or not.
Important Note: Always turn off the ignition before inspecting or replacing fuses.