Fuses are the gatekeeper and sacrificial devices of an electrical circuit. It protects the electrical circuits from overcurrent. It is a crucial and common element in an electrical circuit. Ideally, every electrical circuit should have a fuse.
Sometimes these fuses require testing to check that they need replacement or are still working. These fuses can be tested in many different ways including with and without a multimeter, even without removing them from the fuse box. In this powerful step-by-step guide, you will learn how to test a car fuse with a multimeter.
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How To Test Car Fuses With A Multimeter
Testing a fuse using a multimeter can be the safest way to identify a blown fuse. Some fuses have transparent casings and can easily be diagnosed by visual inspection.
But, some fuses do not have a transparent casing and a fuse’s broken metal element cannot be detected by visual inspection. By using a multimeter you can easily find out a blown fuse. Now In this step-by-step tutorial, I am showing you two methods on how to test a blown fuse by using a digital multimeter.
Method 1. How To Test A fuse Using An Ohmmeter
Method 2. How To Test A Fuse Using Multimeter Continuity Mode
Method 1. How To Check Fuses Using An Ohmmeter
In this method, we will learn how to test a car fuse without removing it using an ohmmeter. But, before we further go, I want to help you understand how an ohmmeter works so that when you test a fuse, you will have no problem diagnosing a bad fuse.
Step 1. Know The Ohmmeter
Resistance is the electrical friction of electric current flow in a conductor. It is measured in ohms. The device, which is used to measure the resistance is called an Ohmmeter. The Ohmmeter reads the open and closed circuit in two different resistive ways.
The Ohmmeter reads the resistance of the open circuit by either 1 Ω or by a non-numerical “OL” value ( Which is pre-programmed in an Ohmmeter).
Where 1 Ω indicates a 100% resistance means full resistance (No-Connectivity or Open Circuit) and “OL” indicates, some call it “Open-Load”, “Open-Loop”, Other calls it “Over-Limit”, or “Open-Line”.
But whatever it denotes, one thing is clear whatever is being measured is not making a path for electric current to flow from the red lead to the black lead of the multimeter (No Connectivity), which means the circuit is open.
On the other hand, the ohmmeter reads “Closed Circuit” in numerical values of zero or near-zero, and in some ohmmeters, the numerical value of “Closed Circuit” is less than 1 Ω (If the highest resistance is programmed “1 Ω” in digital ohmmeter).
Now come to the test procedure.
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Step 2. Connect The Leads In Multimeter
Connect the black probe to the common socket and the red probe should go to the (Ω) omega socket.
Step 3. Set The Scale On Ohmmeter
Turn ON the multimeter and move the dial to the lowest resistance range on ohm mode. Here 200 ohm is the lowest ohm range.
Step 4. Place The Tip Of The Lead On The Fuse
First, place the fuse on a non-conducting material like plastic or wood and touch both leads together to get an initial reading as a standard we will compare it with the fuse test. After that put, both tips of the black and red leads on the fuse terminals.
This is an Info
Fuses are polarity-free safety devices. No matter, whatever tip of the lead can be touched with any terminal of the fuse. You can confidently touch any tip of the probe to any terminal of the fuse.
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Step 5. Measure The Ohmmeter Reading
After touching the tips of both leads to fuse terminals, now look for the ohmmeter readings. If the ohmmeter resistance reading is similar to the reading you touched together the leads, before testing the fuse or if the reading changes to a little low or high resistance values, it means the fuse is good and has connectivity between two terminals.
On the other hand, if the ohmmeter resistance reading does not change and still shows the 1 Ω (100% resistance) or “OL” it means the fuse has blown and has no connectivity between the two terminals.
Step 6. Turn OFF The Multimeter
In the end, turn off the multimeter after testing.
Step 7. Never Use Ohmmeter On A Live Circuit
One important thing you need to know beyond testing the fuse. Never use an ohmmeter on an electrically live circuit. It can kill your ohmmeter.
This is an Alert
Always use an ohmmeter on a dead circuit. It can kill the Ohmmeter.
It is because the ohmmeter itself supplies voltage to the circuit, no other voltage is needed.
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Method 2. How To Test A Car Fuse Using Multimeter Continuity Mode
In this method, you are going to learn how to test a car fuse using multimeter continuity mode. Below is the step-by-step procedure for testing the car fuse with a multimeter.
Step 1. Remove The Fuse From Circuit
First, remove the fuse from the suspected circuit.
Step 2. Select The Continuity Scale On the Multimeter
Turn the selector to continuity scale or radio wave symbol on the multimeter and have a quick test to prove the multimeter is good by touching both leads together to hear a beep sound.
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Step 3. Connect The Leads To Fuse
Place the fuse on a non-conducting material and connect the tips of the black and red leads with both terminals of the fuse.
This is an Info
While testing a car fuse, you can connect either lead with either terminal of the fuse. They are polarity-free (No Restriction).
Step 4. Read The Multimeter Display
y touching both leads of the multimeter with both terminals of the fuse will make a beep sound. If it beeps, the fuse is good.
If it isn’t, the fuse is bad.
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