How do you know if one of the ignition fuse is blown?

You can check if an ignition fuse is blown by visually inspecting the fuse for a broken wire or a discolored appearance. Additionally, you can use a multimeter to test for continuity; if the meter shows no continuity, the fuse is likely blown. If your vehicle exhibits problems starting or the ignition system is unresponsive, it may also indicate a blown fuse. Always consult your vehicle's manual for the specific location and specifications of the ignition fuses.