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Fuse Problems 101: Testing And Identifying Fuse Problems

Enrgtech July 1, 2020


Fuses are mainly located on the plugs of electrical appliances. They are designed to self-destruct whenever there is a power surge or over-current situation. By doing so, the fuse is able to break electrical current from flowing hence saving the rest of the circuit from burning. In this sense, the collateral damage in the event of a surge will be less expensive. There are numerous types of fuses. There are those you can test by just looking at them while others require further tests using a test light or multimeter.

Types of fuses

There are numerous types of fuses. Discussed below are some of the common ones found in consumer electronics;

Cartridge Fuses

They are mostly used to protect electrical appliances like pumps, refrigerators, PCs among others. They possess a high voltage and current rating. The maximum rating available is 600A and 600V. Cartridge fuses are widely used in industries and commercial distribution panels. They are further categorized into to, the heavy duty and the ordinary cartridge fuses.

Blade type and automobile fuses

Blade type fuses come in plastic bodies have two metal caps to fit in the socket. They are mostly used in automobiles.

Other types of fuses that are less popular but are still used to protect circuits include; HRC, axial, SMD, High Voltage and Resettable Fuses.

Steps to testing fuse problems

Step 1: Establish the blown fuse

If it is possible to remove the fuse the better. This way you can remove it and inspect it visually. Ordinary cartridge fuses are particularly easy to inspect. If the ordinary cartridge fuse is blown you will be able to tell that by looking through the glass. For cartridge fuses that have opaque casing and other types of fuses, you will need to use a multi-meter. Set the multimeter to test for continuity or measure resistance.

Test the meter to ensure that it is working properly by touching the leads together until you hear a beep. If the meter is set to measure resistance, you will see 0 ohms when the leads touch. Power off the circuit and then place the leads on either side of the fuse. If you hear the same beep, the fuse is still intact, if you fail to hear the beep, the fuse is blown. If you meter reads OL then the fuse is blown.

If you are not able to easily remove the fuse from the circuit then you can test it by measuring the voltage across it with a digital multimeter. To achieve this, leave the circuit powered and set your multimeter to measure voltage. Take proper precautions to ensure that you are not exposed to dangerous voltages. Place the multimeter leads on either of the fuses. If the potential difference between either side of the fuse is zero, then the fuse is intact. If there is a potential difference between the sides then the fuse has blown.

Step 2: Replacing the blown fuse

It is very important that you replace the blown fuse with one that is identical to the blown fuse. The other thing you also need to pay attention to is whether or not the fuse is a fast or slow blow. It is important to note that you can replace a slow blow fuse with either a slow or a fast blow but not the other way around. To avoid any mishaps, the best thing to do is to replace the blown fuse with an exact one.


Fuses play a critical role in ensuring the safety of the circuit and wiring system. However, they can be very inconveniencing when they blow up. In the event that this occurs, the fault-finding skills discussed above can come in handy in identifying and replacing the faulty fuse.

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Enrgtech is UK’s leading Authorized electronic components distributors. Has millions of electronic components and offers same day shipping. New components added daily..The biggest store of electronic, electrical components and spare parts Search and find anything you need View all posts by Enrgtech →

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