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Amanda Foster — Reviewed writer, former magazine editor

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How to Handle Test Fuses with a Test Light Step by Step

When test fuses with a test light leaves you confused, worried, or unsure what it means, a clear step-by-step approach can help you sort the signal from the stress. This guide explains how to understand the situation, reflect on what matters, choose a practical next step, and know when to ask for trusted support.

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Part 1

Checking Fuse Power in a Vehicle

Find your vehicle’s fuse box panel and remove the panel’s cover.

The fuse box panel is usually located under the hood, underneath or on the side of the dash, in the glovebox, or in the trunk. The fuse box panel is a panel with different colored and numbered fuses. Pry the plastic cover off once you find the panel.

The fuse box panel is usually located under the hood, underneath or on the side of the dash, in the glovebox, or in the trunk.
The fuse box panel is a panel with different colored and numbered fuses.
Pry the plastic cover off once you find the panel.
The fuse box panel is usually located under the hood, underneath or on the side of the dash, in the glovebox, or in the trunk.
The fuse box panel is a panel with different colored and numbered fuses.

Ground the test light’s clip or clamp on a grounded metal surface.

Squeeze the clip or clamp to open it up and place it over the car battery’s negative terminal, a bolt, or another nearby, unpainted metal surface on the vehicle. The test light must be grounded for it to work.

Squeeze the clip or clamp to open it up and place it over the car battery’s negative terminal, a bolt, or another nearby, unpainted metal surface on the vehicle.
The test light must be grounded for it to work.
Squeeze the clip or clamp to open it up and place it over the car battery’s negative terminal, a bolt, or another nearby, unpainted metal surface on the vehicle.
The test light must be grounded for it to work.
Squeeze the clip or clamp to open it up and place it over the car battery’s negative terminal, a bolt, or another nearby, unpainted metal surface on the vehicle.

Poke the tip of the test light’s probe into 1 of the holes on a fuse to test it.

Pick a fuse that you want to test. Hold the test light by the handle and stick the pointy metal tip of the probe into 1 of the 2 round or square holes on the fuse.

Pick a fuse that you want to test.
Hold the test light by the handle and stick the pointy metal tip of the probe into 1 of the 2 round or square holes on the fuse.
Pick a fuse that you want to test.
Hold the test light by the handle and stick the pointy metal tip of the probe into 1 of the 2 round or square holes on the fuse.
Pick a fuse that you want to test.

Wait for the test light to light up to determine whether a fuse is working.

The test light will light up right away when you poke the probe into a working fuse. The fuse is likely blown if the test light doesn’t light up.

The test light will light up right away when you poke the probe into a working fuse.
The fuse is likely blown if the test light doesn’t light up.
The test light will light up right away when you poke the probe into a working fuse.
The fuse is likely blown if the test light doesn’t light up.
The test light will light up right away when you poke the probe into a working fuse.

Test the second hole on the fuse.

Stick the metal tip of the probe into the other hole. Watch for the test light to go on to verify that the fuse is fully functional.

Stick the metal tip of the probe into the other hole.
Watch for the test light to go on to verify that the fuse is fully functional.
Stick the metal tip of the probe into the other hole.
Watch for the test light to go on to verify that the fuse is fully functional.
Stick the metal tip of the probe into the other hole.

Part 2

Testing Home Fuses

Turn off any electronics in the area that you are testing the fuse for.

Turn off all the lights and unplug any electrical appliances from outlets in the room that you want to test the fuse for. This will help avoid electrical surges.

Turn off all the lights and unplug any electrical appliances from outlets in the room that you want to test the fuse for.
This will help avoid electrical surges.
Turn off all the lights and unplug any electrical appliances from outlets in the room that you want to test the fuse for.
This will help avoid electrical surges.
Turn off all the lights and unplug any electrical appliances from outlets in the room that you want to test the fuse for.

Make sure the fuse you want to test is in the “on” position.

Open up your breaker box and locate the switch for the fuse you want to test. Flip the fuse switch on if it is off or partially off.

Open up your breaker box and locate the switch for the fuse you want to test.
Flip the fuse switch on if it is off or partially off.
Open up your breaker box and locate the switch for the fuse you want to test.
Flip the fuse switch on if it is off or partially off.
Open up your breaker box and locate the switch for the fuse you want to test.

Clip the test light’s clip onto the bare metal of the breaker box.

Squeeze the test light’s alligator clip or clamp to open it up, then clip it onto a piece of bare metal on the breaker box that surrounds the fuse panel.

Squeeze the test light’s alligator clip or clamp to open it up, then clip it onto a piece of bare metal on the breaker box that surrounds the fuse panel.
Squeeze the test light’s alligator clip or clamp to open it up, then clip it onto a piece of bare metal on the breaker box that surrounds the fuse panel.
Squeeze the test light’s alligator clip or clamp to open it up, then clip it onto a piece of bare metal on the breaker box that surrounds the fuse panel.
Squeeze the test light’s alligator clip or clamp to open it up, then clip it onto a piece of bare metal on the breaker box that surrounds the fuse panel.
Squeeze the test light’s alligator clip or clamp to open it up, then clip it onto a piece of bare metal on the breaker box that surrounds the fuse panel.

Touch the test light’s probe to the fuse’s screw.

Look for the exposed screw to the left or right of the breaker switch you want to test. Hold your test light by the handle and touch the pointy metal tip of the probe to the fuse’s screw.

Look for the exposed screw to the left or right of the breaker switch you want to test.
Hold your test light by the handle and touch the pointy metal tip of the probe to the fuse’s screw.
Look for the exposed screw to the left or right of the breaker switch you want to test.
Hold your test light by the handle and touch the pointy metal tip of the probe to the fuse’s screw.
Look for the exposed screw to the left or right of the breaker switch you want to test.

Watch to see if the test light turns on to find out if the fuse works.

The test light will light up immediately if the fuse is working properly. The fuse is likely bad if the test light does not turn on.

The test light will light up immediately if the fuse is working properly.
The fuse is likely bad if the test light does not turn on.
The test light will light up immediately if the fuse is working properly.
The fuse is likely bad if the test light does not turn on.
The test light will light up immediately if the fuse is working properly.

Part 3

Trying the Test Light

Connect the test light’s clip or clamp to a metal surface to ground it.

Any metal surface on the car or the car battery’s negative terminal will work for this. Squeeze the clip or clamp open and slide it onto the ground source, then release the clip or clamp to secure it in place.

Any metal surface on the car or the car battery’s negative terminal will work for this.
Squeeze the clip or clamp open and slide it onto the ground source, then release the clip or clamp to secure it in place.
Any metal surface on the car or the car battery’s negative terminal will work for this.
Squeeze the clip or clamp open and slide it onto the ground source, then release the clip or clamp to secure it in place.
Any metal surface on the car or the car battery’s negative terminal will work for this.

Touch the tip of the test light’s probe to a positive power source.

The probe is the metal needle at the end of the cable that has the handle. Hold the test light by the handle and touch the end of this needle against the car battery’s positive terminal or any other positive power source.

The probe is the metal needle at the end of the cable that has the handle.
Hold the test light by the handle and touch the end of this needle against the car battery’s positive terminal or any other positive power source.
The probe is the metal needle at the end of the cable that has the handle.
Hold the test light by the handle and touch the end of this needle against the car battery’s positive terminal or any other positive power source.
The probe is the metal needle at the end of the cable that has the handle.

Watch for the test light to light up to see if it is working.

The test light will light up as soon as you touch the probe to the power source. Proceed with testing your fuses once you are sure that your test light is working properly.

The test light will light up as soon as you touch the probe to the power source.
Proceed with testing your fuses once you are sure that your test light is working properly.
The test light will light up as soon as you touch the probe to the power source.
Proceed with testing your fuses once you are sure that your test light is working properly.
The test light will light up as soon as you touch the probe to the power source.

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