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How to Know When Fuses Are Blown

George Lawrence J.D.

The electricity in your home is carried by electrical circuits. If these circuits overload or surge, the electrical output could damage the appliances and the wiring in your home. To prevent this damage, fuses are installed. Fuses protect electrical circuits by stopping the electrical current flow.

If the surge or overload is too great, the fuse may blow; check your fuses for signs of damage to see if they are blown.

  1. Locate your fuse box. If a series of lights or a certain appliance suddenly stops working, or you notice other indications of a power failure, you need to locate your fuse box to check the fuses. Typically, the fuse box is located in the basement of your home or in your home's utility closet.

  2. Open your fuse box and check the fuses. A common fuse is a screw-in fuse; these fuses have a glass that allows you to check the metal strip inside. If you notice that the metal strip is damaged (such as charred or broken), then the fuse is blown.

  3. Use a multimeter to measure the resistance of cartridge fuses. Cartridge fuses look like shot-gun shells; you can test whether a cartridge fuse is blown by touching both ends of a multimeter to each end of the cartridge fuse. Low resistance is good; high resistance indicates the fuse is blown.

  4. Look for a signal light. Some companies, such as Ferraz Shawmut, manufacture fuses with blown fuse indicators. These indicators attach to the fuse and display a signal light if the fuse is blown. If your fuses are equipped with a blown fuse indicator, examine it for a lit signal light. If the light is on, the fuse is blown.