Content

• Steps
• Part 1 of 2: Fuses and Multimeters
• Part 2 of 2: Checking the Fuse
• Tips
• Warnings

Cars and older homes do not use modern electrical circuit breakers to prevent surges. From time to time it is necessary to check the condition of the fuses in the machines, and this can be done with a multimeter. It is easy to learn how to use it and it does not take a lot of your time.

Steps

Part 1 of 2: Fuses and Multimeters

1. 1 Learn to understand fuses. Fuses are wires that are not designed to last long. Their purpose is to protect valuable electrical appliances and prevent fires (especially in homes) due to power surges. If an overvoltage is applied to the fuse, it will burn (literally) and open the circuit. There are different fuses, but most often they differ only in appearance. Below we provide a description of the most common two types:
   • The cartridge fuse has a cylindrical shape. For many years, these fuses have been used in a wide variety of devices and installed in homes. There is a metal contact on each side of such a fuse, and the fuse itself is a tube with a wire inside.
   • Flat fuses have been used in cars for the past 20-30 years. They vaguely resemble a plug of a wire, because they have two metal pins protruding from the plastic, under which the wire is hidden. Cars used to have small fuses in glass cartridges. The flat fuses fit neatly into the space provided for them, and very little space is needed to install a large number of these fuses.
2. 2 Understand how a multimeter works. Multimeters allow you to measure AC and DC voltage, resistance and current. To check the condition of a fuse, you can use a multimeter, an ohmmeter (a device that measures resistance), or an ammeter (a device that measures amperage).
   • The multimeter has two contacts: positive and negative. When measuring resistance or current, the instrument will release a small amount of electricity from its battery and measure how much will pass through the circuit of the selected item.
3. 3 Understand why fuses are tested. This is the easiest way to find out if the network is OK in your car or home, so it is very important to know how to use a multimeter.
   • Checking fuses is easier than checking electrical appliances. There are many complex devices in the car and in the house. In addition, many of the elements in the car can only be checked at service centers, and it will not be cheap. It is easy to check the fuse with a multimeter, and the device itself is inexpensive and easy to use.
   • Many fuses are designed so that the user can see if they are working properly. They use transparent plastic to make it clear if the wire is intact. If the plastic is darkened, usually this means that the wire is burnt out. However, in some fuses, the plastic darkens even after a few small overheats, which may be the consequences of a power surge that occurred several weeks or months ago. If the device does not work, check the fuses. If they are ok, there is most likely a problem with the instrument itself, so you will need to contact a repair technician.

Part 2 of 2: Checking the Fuse

1. 1 Turn off the engine (if it is a car) or turn off the device and only then remove the fuse. Make sure that the appliance, device or vehicle is turned off before removing the fuse. To remove the fuse, simply pull it straight out of the socket.
2. 2 Turn on the multimeter and set it up. You can install a multimeter to Ω (or OM). This will measure the resistance. Before you start checking the fuse, connect the positive and negative ends and see the result.The number that appears on the screen should be close to the measurement you get when checking the fuse.
   • You can measure the amperage by selecting the arrow icon on the multimeter that moves along the line.
3. 3 Place both ends of the multimeter over the fuse and look at the screen. The fuse is actually a single wire, and there are no complex elements in it, so don't worry if you align the contacts correctly.
4. 4 Check fuse. If you are using a multimeter to measure resistance, the value obtained should be the same or very close to the value you got when you connected the two pins of the meter at the very beginning. If the fuse is blown, nothing appears on the screen or the message "O.L." (overload) - it all depends on the brand and type of multimeter used.
   • If you are using a digital multimeter configured to measure current, the multimeter should beep all the time when the two wires of the multimeter and the fuse are in contact. This will mean that the chain is not damaged. If not, the fuse has blown. Always test the function of your multimeter before using it by connecting the test leads together. If you hear a beep, then the multimeter is working properly and is ready for use.

Tips

• Cars usually use colored flat fuses. If you look at them from above, you can see through the transparent case whether the metal strip inside is intact (the fuse is good) or damaged (the fuse is blown).
• Not just fuses are installed in electrical panels in houses, but modern circuit breakers ("automatic machines"), in which there are no fuses, but they are much safer. Consider replacing your old system with a new one.

Warnings

• Do not check the fuse while the appliances are on.
• Do not replace a blown or suspicious fuse with a stronger one. The characteristics are calculated based on safety, therefore the fuse should be replaced with a similar or even slightly weaker one.