How to test a car fuse with multimeter

In this tutorial, we will explain how to test a car fuse with a multimeter effectively. Further, we will describe what is a fuse, what are types of fuses are, effective tips for learning about fuse importance and usage.

Differences Between a circuit breaker and a fuse

Both smart circuit breakers and fuses are used in cars and homes to cut the flow of electricity during power surges. Their usage purpose is not different, but their working principle is different from each other. A fuse has a metal that melts during the power surges to cut the flow of electricity on the other hand the circuit breaker works on the switching mechanism to handle the power surges.

A fuse is a crucial component for any electrical wiring system safety. It is important to test that a fuse is fine. To remove doubts and dangers in any electrical circuit about fuse condition, we use a special instrument called a multimeter to test the fuse, which is not difficult to use.

Precautions:

Every fuse has a specific rating depending upon the electrical circuit in which is going to be used. Fuse rating defines how much current it will allow passing through it. Never replace a fuse with a blown-out fuse or a fuse that has a higher rating than the older one. A fuse that has a smaller rating can be replaced with the blown-out one.

Don’t test the fuse, when the current is passing through the circuit in which a fuse is placed.

What is a fuse?

A fuse has a metal that melts during the power surges to cut the flow of electricity. Metal inside the fuse is surrounded by the plastic that completes the circuit when placed in. During the power surges, the fuse cuts the power supply in the circuit, thus saving the other expensive electronics from getting harmed or damaged, connected to the circuit.

Metal inside the fuse blows when more current runs through the circuit than the normal range. This extra current melts the metal wire inside the fuse, thus cutting the circuit. When the circuit breaks, extra power can’t get to the central part of the circuit that can’t handle it. In-car, there are two places where the fuse is commonly placed. One under the car bonnet, there will be a box where all the fuses are placed, second under the dashboard on the passenger side.                                                                                                                 

Types of fuses

There are different fuses available in the market. Some fuses have different colours on their body and each colour indicates how much current it can allow to pass through it. Grey colour fuses commonly can handle high power.

On the small fuses, we can see through the colour on the fuse whether the fuse is blown out or not without testing it with any instrument. Colour distortion on the fuse also gives the hint that the fuse has blown out and it’s time to replace it. In fuses that have a much higher rating, the wire will not be visible. If you think the fuse is not working, you will need to test it with a multimeter.

How do we know the fuse blows?

Here are common ways through which we can find out fuse is working or not. First, in your car trace the fuse that controls the device which is not working. This information you can find out on the car’s manual, there will be a diagram on the fuse box, or you can find this information online. Then remove the fuse from the circuit with the help of an electronic instrument. See precisely to find out the signs of colour distortion or melted wire. Then you should buy a new car’s fuse to replace the damaged one.

 How to test a Car Fuse with a Multimeter?

Following are important steps to test a car fuse:

  • First, pull the fuse from the concerned circuit. Then check it with the naked eyes. Check through the plastic whether the fuse wire is broken or not.
  •  If you can’t see the wire through the plastic, then it’s time to check the fuse with the help of a multimeter. Bring the multimeter on the spot, and take its probes out for the connections.
  • Set the dial of the multimeter towards the resistance measurement by pressing the function button on the multimeter.
  • First connect the two probes of the multimeter together, before making connections with the fuse, to get the baseline readings. When you have an idea of reading then it’s time to connect the multimeter’s probes with fuse ends.
  • Connect one wire of the multimeter with one prong of the fuse and the other probe or wire with the other prong of the fuse and note the resistance readings. If the noted resistance readings come close to the earlier readings; when the two probes are touched together, then the fuse is fine.
  • If the multimeter gives no reading when the multimeter’s probes are properly connected with the fuse ends, then the fuse is not working and it’s time to replace it with the new one.
  • Current passing through the fuse is not able to make it back, which is the reason the multimeter gives no reading.
  • To ensure the fuse is blown, there is also another method to check it with the help of a multimeter.
  • This time set the dial of the multimeter towards the current measurement instead of ohm by pressing the function button on the multimeter.
  • Touch the probes of the multimeter with the ends of the fuse properly.
  • If the multimeter makes the beep sound, then the current is able to flow through the fuse successfully and the fuse is fine.
  • If the multimeter makes no beep sound, then the current is not able to flow through the fuse, and the fuse has blown. Both of the above describe methods are acceptable for testing the fuse.

How to Replace a Car Fuse?

If the fuse is damaged, then it is simple. Replace it with the new one, which has the same rating.

On the other hand, if the fuse is working properly, then you have to look deeper to find out the problem in the electrical system.

If the electrical system in your car or home has more than one fuse. It’s better to trace them all and test with the multimeter first to find out which fuse has blown out.

What are the possible causes of the car fuse blowing?

Fuse is an integral component of any electrical system. A fuse protects the circuit from power surges. A blown fuse indicates that the circuit is the short one. Following are the important causes of blown-out fuse:

You mistakenly plug the wrong bulb in the headlights or the backlights.

Accessories that are already shortened like the cigarette lighter socket plugged in the power socket or the small metal object such as coin fall inside the socket.

A wire that is connected to the engine component, rubs through it, which will subsequently blow out the fuse.

Frequently Asked Questions

Can you check car fuses without removing them?

There are some fuses, that can be tested inside the circuit, without removing them from the circuit. These fuses have contact points on the top of their body. For example, flat-bladed type fuses.

Can blowing a fuse cause a car not to start?

If the fuse is blown out, it will cause a small problem in the car’s electrical system. For example, the headlight or the taillight is not working, inside light is not functioning, radio is not running, etc. Chances are less than a car would not start if the fuse has blown out.

Conclusion

By reading the above article, you will be able how to test a car fuse with a multimeter effectively. And you will also be able to find out whether it is the fuse or any other electrical component that is not working efficiently.

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