Fuse Replacement Fuses are all through your house--and rightly so. They are the weakest link in the chain for good reason. They keep electricity surges from damaging appliances and circuits. Fortunately, they are also easy to test and to replace. Here's how the Fix-It Club fixes fuses. (Refer to the electrical Service Panel Fix-It Guide for household electrical circuit fuses and circuit breakers.) How Does It Work? An appliance fuse is an electrical safety device with a metal strip that melts and interrupts the appliance's electrical circuit when the circuit is overloaded or the appliance overheats. Electrical fuses protect electrical devices from electrical overloads. Thermal fuses protect them from overheating. Electrical fuses are mounted on the outside of the unit in a screw-out receptacle marked "Fuse," or inside the unit near the cord and/or a power supply. Thermal fuses typically are installed inside an appliance on or near one of the electrical cord wires. Fuses are clipped, screwed, or soldered into place. Most fuses open a few seconds after a substantial overload begins. Slow-blow fuses are designed to protect equipment where heavy, periodic demands for current would blow a common fuse even though the apparatus is operating normally. Quick-blow fuses open at even a momentary Many appliances and electronics overload; they are used to protect delicate or sensitive have fuses that are accessed components. without opening the housing. What Can Go Wrong? A fuse can blow, meaning the metal within the fuse casing (usually glass) melts and interrupts the electrical circuit. An appliance or a portion of an appliance will not operate once a fuse has blown. The purpose of a fuse is to stop operation of the appliance or electronic component before the unit is damaged.