How to Check Fuses

The purpose of a fuse is to stop higher than normal current from flowing on a circuit. A fuse is designed to protect equipment from getting damage and from overheating, and potentially causing a fire. There are generally 2 sizes of fuses, a chip-style fuse and a cylindrical fuse. The chip-style fuse, which is 1.25 by .25 inches (3.2 cm by .6 cm), is typically used in automobiles. The cylindrical fuse can be found in electrical equipment. Fuses can range in current rating from a fraction of an amp to hundreds of amps. There are also 2 types of fuses, fast-acting and slow-blow. Fast-acting fuses will blow very quickly when the current rating of the fuse is exceeded. Slow-blow fuses are designed to blow when there is a continued overload on the circuit, such as a short circuit. The slow-blow fuses are designed not to blow when there is a temporary current spike. Checking whether a fuse is good or bad is a very simple process and is something everyone should know how to do

Steps

1.       Inspect the fuse. When a fuse is blown, you may see several indicators. 

• Check to see if the very fine wire in the fuse casing is broken with no discoloration to the casing. This most likely indicates that there is no major short on the circuit.

•   Look to see if the very fine wire in the fuse casing is broken with slight discoloration to the fuse casing. This, again, most likely indicates that there is no major short on the circuit.

•  Verify that the very fine wire in the fuse casing is broken and the casing is discolored. This indicates that there is a major short on the circuit. 

2          Find a multimeter to use to check the fuse. A multimeter is a tool used frequently when working with electricity.

3.         Set the multimeter to the Ohms setting.

• Place 1 of the leads of the multimeter to 1 end of the fuse. Place the other lead of the multimeter to the other end of the fuse.
• Read the multimeter. If the fuse is not broken, you will get a resistance reading on the multimeter. If the fuse is broken, you will not get any reading on the multimeter.

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