How to Use a Fuse Tester on a Car
8 Minutes Read
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 out of the fuse box.
In this powerful step-by-step guide, you will learn The Seven different fast and easy methods to test a car fuse with pictures. Three test methods are without a multimeter and four tests are with a multimeter.
This page is divided into two sections with seven different methods to test a fuse. Three test methods are with a multimeter and four methods are without a multimeter.
Without Multimeter
- Method 1. Visual Inspection
- Method 2. Shifting The Fuse
- Method 3. Using Test-Lamp
With Multimeter
- Method 4. How To Test A fuse Using An Ohmmeter
- Method 5. How To Test A Fuse Using Multimeter Continuity Mode
- Method 6. How To Test A Fuse Measuring The Voltage
- Method 7. Testing The Fuse With Multimeter Using Body Frame Method Without Removing From Fuse Box
Without Multimeter
Method 1. Visual Inspection
This method of testing a car fuse without multimeter involves checking the metal element of the fuse visually out of the fuse box.
A good fuse has a metal element bridge from one end to another end encased in a semi-transparent plastic housing, which is visible from the outside, where you can detect a blown fuse.
On the other hand, a blown fuse has a broken metal element bridge between two terminals.
To know how to inspect the fuse visually first safely remove the fuse from the circuit through a plier or fuse puller and visually inspect under good light.
You will see a metal bridge across two terminals.
If you could see it. It means the fuse is good.
But, if you could see a broken bridge. It means the fuse has blown.
One important point you need to know that it is easier to spot a break in the metal element of a higher amperage rating fuse than a lower amperage rating.
I have already mentioned this point in my article that the metal element size varies based on the amperage rating of the fuse.
The higher the amperage rating the more width the fuse metal element has.
It means you can quickly figure out a 30 amp blown fuse than a 0.5 amp blown fuse.
This is an Alert
It is easier to spot a break in the metal element of a higher amperage rating fuse than a lower amperage rating. The higher the amperage rating the more width the fuse metal element has.
This is an Alert
Bear in mind, some glass tube fuses are blackened due to the blowing, and it is hard to spot broken metal elements in the fuse due to its dirty housing case.
Method 2. Swapping The Fuse
This is another method of testing a car fuse without a multimeter.
In this method, you can check an automotive fuse without a multimeter by swapping.
You can quickly identify a good or bad fuse by exchanging a good fuse with a suspected fuse in a good working circuit within the car.
First, find out a good working circuit of the amperage rating fuse similar to the suspected fuse.
Remove the suspected fuse and put it in a good working circuit.
Now, look at the circuit, if the circuit works with the suspected fuse.
It means the fuse is good. The problem might be somewhere else in the circuit.
If the good circuit doesn't work with the suspected fuse.
It means the fuse has blown.
This Is A Caution
Don't put the good fuse in the suspicious fuse's circuit, you might blow the fuse or the chances are that the circuit can burn.
Method 3. Testing The Fuse Using Test Light
This is another way of testing a car fuse with a test light. It is one of my favorite methods of testing the car fuse because it is very easy to use.
It is the last method of testing a car fuse without a multimeter. In this method, we will use a test light to identify a good or bad fuse.
This method of testing involves flashing test lights in both terminals of the fuse.
This Is A Note
This procedure can only be performed on fuses present in the live circuit.
Step 1. Turn ON The Suspected Circuit
Switch ON the suspected fuse's circuit.
Step 2. Connect The Test Light With Battery & Fuse
- Place the negative pole of the test light on the body frame or on the battery negative terminal
- Place the second pole on fuse terminals one by one (Terminals are exited from the upside of the blade fuse casing) .
Step 3. Look At The Test Light Flashing
If the test light flashes in both terminals of the fuse, It indicates the fuse is good.
If the test light flashes in O ne terminal of the fuse and not in the other terminal, it means the fuse has blown.
With Multimeter
Testing a fuse using a multimeter can be the safest way to identify a blown fuse.
Some fuses have a transparent casing 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 how to test a blown fuse by using a digital multimeter.
Method 4. How To Test A fuse Using An Ohmmeter
In this method, we will learn how to test a car fuse using an ohmmeter.
But, before we further go, I want to make you understand how an ohmmeter works so 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 used to measure the resistance is called 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", "Open-Line".
But whatever it denotes, one thing is clear that whatever is being measured is not making a path for electric current to flow from the red probe to the black probe (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 ohmmeter 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.
This Is an Info
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). On the other hand, the ohmmeter reads "Closed Circuit" in numerical values of zero or near-zero.
Step 2. Connect The Leads In Multimeter
Connect the black probe in 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 Fuse
First of all, 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 probe can be touched with any terminal of the fuse. You can confidently touch any tip of the probe to any terminal of the fuse.
Step 5. Measure The Ohmmeter Reading
After touching the tips of the 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 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 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.
Method 5. 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 of testing the car fuse with multimeter.
Step 1. Remove The Fuse From Circuit
First, remove the fuse from the suspected circuit.
Step 2. Select The Continuity Scale On 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.
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
By 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.
Method 6. How To Test A Fuse Measuring The Voltage
This is another method of testing a car fuse with a multimeter.
In this method, you will learn how to test the car fuse without removing them from the fuse box.
In this testing method, voltage is measured in both terminals of the fuse with a multimeter without pulling them out of the fusebox.
If the voltage is measured in both terminals of the fuse then the fuse is good and if the voltage is measured in one terminal of the fuse, not in another terminal then the fuse has blown.
Step 1. Move The Dial To DC Volt Mode
Grab the multimeter and move the selector to 20 volt DC mode and put the black lead in the common socket and red lead in the Voltage socket.
Step 2. Turn ON The Suspected Fuse's Circuit
Turn ON the suspected fuse's circuit. So that the electrical current starts to flow in the circuit, and voltage is measured across the fuse using a digital voltmeter.
Step 3. Check The Fuse
Place the tips of both leads on fuse both terminals and look at the display of the voltmeter.
You will see zero or near-zero voltage, it means the fuse is good.
If the voltage across the fuse is the full supply-voltage, it means the fuse has blown. Need replacement.
Method 7. Testing The Fuse With Multimeter Using Body Frame Method
You can also test the fuse the other way around by putting the black probe of the multimeter on the battery negative terminal or body frame and the red probe on the fuse terminals one by one.
Check the multimeter reading, if the voltage is full supply-voltage in both terminals of the fuse this indicates a good fuse.
If the multimeter reads full supply-voltage in one terminal and does not read full supply-voltage in the second terminal, it means the fuse has blown.
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How to Use a Fuse Tester on a Car
Source: https://www.easycarelectrics.com/test-a-car-fuse/
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