If you’re working on a car, truck, or another piece of machinery that uses fuses as part of its safety system, you may need to test the fuses from time to time. These devices can blow when too much current passes through them, protecting the rest of the system from potential damage. Knowing how to test a fuse with a multimeter is an important skill if you want to check its operation or replace one because it’s blown. If you have an electrical problem with your car, RV, or another piece of machinery and aren’t sure why checking the fuses is a good first step. They are often tripped by heaters or by some other minor electrical issue that isn’t enough to be concerned about but is enough to trigger the fuse. The multimeter will let you know quickly if they are blown so that you can move on to diagnosing something more major.
How To Test A Fuse With A Multimeter
- Connect a multimeter in the range of 20 to 200 volts DC. If you don’t have a multimeter, you can use a voltmeter instead.
- Place the red lead on the fuse and the black lead on GND.
- Set your meter to read DC voltage (for example, with an LED setting). Read the voltage across your fuse for at least five seconds, or until your meter indicates that it has stabilized to zero. You should see a reading between 0 and 5 volts DC for most fuses. A reading of about 2 volts is within normal limits for most fuses, although some will read higher or lower depending on their design and construction. If you get no reading at all from your fuse when you test it with this method, then it may be broken or damaged and needs to be replaced. It’s also possible that there is something wrong with how your meter is functioning or that something else is interfering with it (such as moisture in the air). It’s almost certainly not broken without being able to test it again when you are sure everything else is safe before moving on to other things.
- If you have a digital multimeter, turn off its display (if it has one) so that it only reads DC voltage, and then check each pin individually until you find one that shows an open circuit (meaning there is no connection between two points) or a very low resistance (meaning there is a very small amount of current flowing through the fuse).
- If you have a dial multimeter, turn off its display so that it only reads DC voltage, and then check each pin individually until you find one that shows a very low resistance.
- If you have any other type of multimeter, follow the instructions on the back of it to find out what type of range setting it has, or use the instructions in your owner’s manual. The important thing is to get a reading from one pin at least for five seconds or longer before moving on to the next pin.
- If you are doing this with a digital multimeter, set both ranges (for example, DC volts and AC volts) to 20 volts DC and then check each pin individually until you find one that shows an open circuit or a very low resistance (see step 5). It will be easier if you do this with all five pins on your multimeter than if you do it one at a time because if your meter doesn’t show an open circuit when testing the first one or two pins, then chances are good that it will show an open circuit when testing all five pins later on. You can also use this method with just four pins and just look for one reading in each range (for example, three readings in AC volts and two readings in DC volts), but don’t expect to get any reading at all from some fuses if they are blown.
- If you have a dial multimeter, set both ranges to 20 volts DC and then check each pin individually until you find one that shows a very low resistance (see step 5). It will be easier if you do this with all five pins on your multimeter than if you do it one at a time because if your meter doesn’t show an open circuit when testing the first one or two pins, then chances are good that it will show an open circuit when testing all five pins later on. You can also use this method with just four pins and just look for one reading in each range (for example, three readings in AC volts and two readings in DC volts), but don’t expect to get any reading at all from some fuses if they are blown.
Other Ways To Test A Fuse:
Installing a Fuse
A fuse is a device that is installed into a circuit to protect it from blowing out. They are made of a special material that melts when too much current flows through them. They are designed so that they will melt rather than the wiring being used in the circuit. If you are testing a fuse, you are likely replacing one that is blown. To install a new fuse, you will first have to locate the circuit in question. There will be a diagram of the fuse box on the back of the fuse box. The fuse box is usually located near the circuit you are working on but not always. It can be anywhere on the machine you are working on. Once you have found the fuse box, you will want to open it up and look for the circuit you are working with. The fuses will be labeled with numbers corresponding to the circuit they are protecting. You will want to remove the blown fuse and replace it with a new fuse of the same rating.
Testing a Fuse with Continuity Tester
A continuity tester is a type of multimeter that can be used to check to see if a circuit is complete. A circuit is complete when the electrons can flow freely through it without interruption. If there is a break in the circuit, electrons won’t be able to flow through it. A continuity tester will have a pair of probes that you can touch to the ends of the circuit you are testing. If the circuit is complete, the multimeter will show a reading of “0”. If there is a break in the circuit, it will show a “1” or some other number to indicate that the circuit isn’t complete.
Testing a Fuse with an Ohm Meter
A fuse may be blown because too much current is flowing through the circuit it is protecting. If this is the case, you will want to test the resistance of the circuit to make sure it is close to what it should be. The ohm meter on your multimeter will allow you to do this. The ohm meter measures the amount of resistance in a circuit. It will tell you whether there is too much or too little resistance in the circuit. If the resistance is too low, you may have a short circuit. If the resistance is too high, a fuse may be blown. You will test a fuse by touching the probes of the ohm meter to the ends of the circuit. It will give you a reading depending on the resistance of the circuit. If the fuse is blown, the reading will be lower than it should be.
Alternatives to the Multimeter-Based Methods
You can test a fuse for continuity with a simple continuity tester. You will touch the two probes to the two ends of the circuit. You will see a reading of either “1” or “0”. If the fuse is blown, the circuit won’t be complete. If the fuse is blown, it won’t be complete. If you need to find the resistance of a circuit, you can use a multimeter to find the resistance. You will again touch the probes to the two ends of the circuit. You will see the resistance on the screen of the multimeter. The resistance of a blown fuse will be lower than it should be.
Wrapping up
A fuse is a device that is installed into a circuit to protect it from blowing out. They are made of a special material that melts when too much current flows through them. They are designed so that they will melt rather than the wiring being used in the circuit. If you are testing a fuse, you are likely replacing one that is blown. To install a new fuse, you will first have to locate the circuit in question. There will be a diagram of the fuse box on the back of the fuse box. The fuse box is usually located near the circuit you are working on but not always. It can be anywhere on the machine you are working on. Once you have found the fuse box, you will want to open it up and look for the circuit you are working with. The fuses will be labeled with numbers corresponding to the circuit they are protecting. You will want to remove the blown fuse and replace it with a new fuse of the same rating.
