Below I will teach you how to check a fuse with a multimeter. It is also necessary to look inside the fuse to really get into the nitty gritty and see if it’s blown. I will teach you how to do both below.
Important steps we’ll go through:
- Considering the voltage of a fuse.
- Measuring the number of ohms
- Checking fuses in a fuse box
- Measuring resistance if a fuse is blown
- Checking the current state of the circuits
If you have a reading between 0 – 5 Ω (Ohms), the fuse is good. Any higher reading means a bad or degraded fuse. if your reading is OL (Over the Limit) that definitely means a blown fuse.
How Do You Check if a Fuse is Blown with a Multimeter?
In this case, checking whether a fuse is blown using the eye test only may not be sufficient. So you should use a multimeter to eliminate all doubt.
The best idea is to perform an electrical test and test what has happened with a fuse.
- First of all, you must have continuity mode in your multimeter. Most of the best multimeters now have this mode of use. Then, one of the probes must be placed at one end of the fuse. Of course, the other probe of your multimeter must also be placed at the other end of the same fuse.
- Here the main objective is to detect whether the fuse is in good condition. So, in continuous mode, the multimeter should beep to indicate continuity.
- If you can test continuity, the fuse is not blown. In other words, it means that no connection is damaged or broken.
- On the contrary, it could be that the multimeter indicates a high level of resistance without making a sound. So, when this happens, the main reason is that the fuse is already blown and, therefore, not useful.
- You can also use a multimeter’s ohmmeter if it does not have a continuity mode. So, you must select the ohmmeter and place each waveform at each end of the fuse.
- If the fuse is not damaged, the ohmmeter reading should be low. Conversely, the reading will be very high if the fuse is damaged or blown. (The fuse is good if you have a reading between 0 – 5 Ω (Ohms). Any higher reading means a bad or degraded fuse. If your reading is OL (Over the Limit), that means a blown fuse.)
How Do You Check if a Fuse is Bad?
Here, checking if a fuse is good will allow you to save a lot of common contingencies. However, a good fuse is not always available, so you should learn how to test the status of a fuse. You can use a multimeter or detect at a glance if a fuse is completely blown.
It is not very difficult to detect a blown a fuse. Sometimes the main connector of the fuse is melted or broken.
If you can’t guarantee this, you can continue using a multimeter. Usually, when a blown fuse has a broken connector, there’s nothing left to do that can fix it. Conversely, a fuse is fine if the internal connector is not melted. This connector must be in good condition from one side to the other of the fuse.
Obviously, it would be best if you had a new fuse to replace the blown fuse. Of course, there are a lot of fuses available on the market. So, you should also ensure that the new fuse is the same type as the old one.
How Do You Test a Fuse and Relay with A Multimeter?
- To test a fuse with a multimeter, you must use the continuity mode on your multimeter.
- It would be best if you connected the multimeter probes to each end of the fuse. If you can detect continuity on your multimeter, the fuse is good. Conversely, it’s a blown a fuse if you don’t detect continuity in your multimeter.
- On the other hand, you can test whether a coil relay is in good condition or not. It would be best if you also had a digital multimeter with seven functions to do this.
- In this case, you must use the resistance mode between each relay pole. Here the readings must be zero ohms in the corresponding pole of all the contacts. (1)
- At the same time, the contacts in that area should also be viewed as an infinite resistance reading if you locate the probes in the corresponding pole. You can then continue after energizing the relay. You will hear a clicking sound when the relay is energized.
- You will then have to repeat the procedure using your multimeter. Here the resistance of the NC and NO contacts must be adequate. You can also test the solid-state relays with your multimeter. (2)
- In this case, you need to have the diode reading to test this type of relay. The multimeter will read the voltage applied to the relay. The meter will read zero or OL when a relay is not working.
- Conversely, a relay that is in good condition should give a result of 0.5 or 0.7, depending on the type of relay.
- Solid-state relays are usually cheaper and easier to fix.
We have other HOW-TOs articles that you may want to check and bookmark for future reference. Some of these are: How to Tune an Amp with a Multimeter and How to Use a Multimeter to Test Voltage of Live Wires. We hope this learning guide helps you.
References
(1) coil – https://www.britannica.com/technology/coil (2) solid-state – https://electronics.howstuffworks.com/question558.htm
