Types of Test Light and How To Use A Test Light?

Knowing how to use a test light is a skill that will come in handy at a point in time. A test light, which is also known as a test lamp, main tester, or voltage tester, is an electronic tool used to verify the presence of electricity in your car’s circuits. So why do you need a test light?

Your car is made up of an electrical system with various components connected with an organized set of wires, connectors, and terminals. When any of these components develop a fault, your car’s electrical system is affected, and ultimately, your car’s performance takes a hit. Based on the wiring system, it is difficult to know which of the electrical components is faulty. That’s where an automotive test light comes into play. With the right knowledge of test lights, you can detect which of the components is faulty. Read on to find out more about test lights.

How Many Types of Test Light Are There?

The first step to mastering the use of a test light is to understand the types of test lights. There is a range of test lights out there, so knowing their functions lets you choose the best automotive test light for the task at hand. Some are designed for only basic functions, while others are used for a range of electrical functions. Here are some of the test flights that are out there.

how to use a test light on fuses

Non-Contact Voltage Testers

This kind of tester allows you to test for voltage without coming in contact with your car’s electrical components. It is battery-powered and quite easy to use.

Neon Voltage Testers

This test light is designed to detect the presence of voltage alone. It also requires contact with the components, so you’d need to be careful when using it. It is a good substitute for the no-contact test light.  

Plug-In Circuit Testers

This tool has three neon lights that light up in different patterns, each of which specifies a particular test outcome. You can easily interpret what the light patterns mean.

Continuity Tester 

This test light is battery-powered and is great for diagnosing a range of electrical faults. It also comes with an LED digital display that relays information to you.


Test light vs. multimeter? Both tools detect voltage. It is just that the multimeter is used to perform a range of functions. It is built with a dial for fixing the test function, and when used correctly, the multimeter can offer a range of information on different car components. So you may not need too many test lights when you have a multimeter.

Solenoid Voltage Tester

 This is another test light that is designed to execute a range of testing functions. It is not battery-powered and is also inexpensive. It indicates the presence and amount of voltage by either increasing or decreasing its clicking or vibrating.

Digital Clamp Meter

 This tool can function as a multimeter and a current sensor. Although it is a bit pricey, this test light is easy to operate and safe to use. 

How To Use A Test Light

Knowing how to use a test light will help you detect when vital electrical components have gone bad. There are different uses of test lights, so we will be describing how you can use a test light in these scenarios.

how to use a test light to find a short

Positive Voltage Test

The first step is to check if the test light is working. This would require you to clamp the test light to a known ground source. In this case, a ground source refers to exposed metal parts that are part of the car’s chassis. You might also use the battery’s negative terminal. Use the probe to lightly touch a source of positive voltage like a fuse or the positive terminal of the car battery. If the test light lights up, then it is in good working condition.

The next step would be to repeat the same process you followed when testing the test light. The only difference is that after connecting to a ground source, you connect to the end of the wire or the component you are testing for positive voltage. If the tool lights up, then there is some positive voltage present. If it doesn’t, then the component has gone bad and should be cleaned or replaced.

Using Test Light On Fuses

You can use a test light to determine which of your car’s fuses have power or not. Here are the steps to follow. Locate your car’s fuse box panel. You might have to use the owner’s manual to do this. Once you have done this, remove its cover to uncover the fuses. Make sure that the car is not on before you proceed. You then clamp the test light’s clip on a good ground source like a metal surface of the car that does not have paint on it (like a bolt, for instance). The negative terminal of the battery is also a great substitute. It all depends on where the car’s fuse box panel is situated. 

The next step would be to use the list of fuses on the inside of the cover to ascertain which fuse you want to check. Once that is done, insert the test light’s probe into one of its holes to test it. If the fuse is working, the test light will light up. If it doesn’t, then the fuse is most likely bad.

You will need to confirm this, and to do that; you should test the second hole on the fuse. Both holes represent the fuse’s power input and output. If the test light does not light up after testing both holes, then the fuse is most definitely bad and should be replaced.  

Checking for Short to Ground with Test Light

You might notice that your car has begun to lose power. If after checking other aspects of its operations and the problem persists, you should check the electrical system. The idea is to verify the level of electrical resistance, and the best way to do that is to check your car’s ground circuit. Here is how to go about that.

Confirm that the positive circuit is functional. Once this has been ascertained, you can then test the ground circuit. To do this, you’d need to connect one end of the test light(preferably a circuit tester) to the positive end. You then touch the other end of the tester to the ground wire of the component being tested. As always, if the test light lights up, the ground circuit is fine, and you might need to check elsewhere to find the cause of the increased resistance.

Final Words

Test lights are great tools to have in your tool kit. Indeed, knowing how to use a test light is a skill that everyone who owns or uses a vehicle must have. This is because it allows you to ascertain the car’s electrical system and its components easily. This way, you know when the problem is not from the electrical system. So next time your car develops a fault, you should be able to use your test light to eliminate some of the improbable causes of the car’s problems.

Read More:

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts