Signs of a blown fuse in your AC system include a lack of power to the unit, even when the thermostat is set correctly, and other electrical components in your home are functioning properly. You might notice that the AC unit is completely unresponsive, with no signs of operation such as humming or fan movement. Upon inspecting the fuse, you may see visible damage or burn marks, indicating it has blown. Replacing a fuse requires matching the new fuse’s rating to the old one, ensuring safe and proper operation. However, if the new fuse blows shortly after replacement, it suggests an underlying issue within the system, such as an electrical short or overload, necessitating professional evaluation and repair.