What’s an Automotive Test Light and How to Use It. A Beginner’s Guide
When it comes to fixing automotive electrical systems, having the right tools is essential. One of the most useful tools for automotive technicians and DIY mechanics is an automotive test light. In this article, we’ll explore what an automotive test light is, how it works, and how to use it to diagnose electrical problems in your vehicle.
What Is an Automotive Test Light?
An automotive test light is a tool used to test the electrical circuits in a vehicle. A test light consists of a pointed probe that allows you to touch fuses, terminals, or anything else you want to test for power.
An alligator clip clamps to a good ground point on the vehicle, and inside of the handle there is a simple bulb and socket, newer test lights use an LED instead of a standard light bulb. The concept is the same for either option.
The tip of an automotive test light is used to touch the wire or electrical component being tested, if the component being checked has 12 volts going to it the power runs through the automotive test light, through the bulb, and back to the ground point. This illuminates the bulb, if the light bulb illuminates, there is a complete circuit.
How Does an Automotive Test Light Work?
An automotive test light works by simply completing an electrical circuit. When the probe of the test light is touched to a wire or electrical component, it completes the circuit and allows electricity to flow through the light bulb in the handle to the ground. If the circuit has good power and ground, the light bulb will illuminate, indicating the circuit is functioning properly. If the circuit is incomplete, the light bulb will not illuminate, indicating that there is a problem with the circuit.
When Should You Use an Automotive Test Light?
An automotive test light is a versatile tool that can be used to diagnose a variety of electrical issues in your vehicle. Here are some common scenarios where you might use an automotive test light:
- Testing for Power – If you suspect a component is not receiving power, you can use an automotive test light to test the circuit and see if power is reaching the component.
- Testing for Ground – If a component is not working properly, it could be due to faulty ground. An automotive test light can be used to test the ground and see if it is properly connected.
- Testing for Short Circuits – If a fuse keeps blowing, it could be due to a short circuit. An automotive test light can be used to test the circuit and see if there is a short.
With a general knowledge of electrical circuits and an automotive test light, you can fix many electrical issues. This makes an automotive test light a must-have tool for any garage.
How to Use an Automotive Test Light?
Using an automotive test light is simple. Here are the steps you’ll need to follow:
Step 1: Connect the Alligator Clip – Attach the alligator clip to a known good ground source, such as the negative battery terminal or a bare metal surface on the vehicle.
If the circuit you are testing does not light up the test light always double-check the ground. Many people make the mistake of thinking voltage is always the issue with automotive electrical circuits, a good ground is just as important, no ground, no electrical circuit.
Step 2: Touch the Probe – Touch the probe to the wire or component you want to test. This can be anything from a fuse to a wire. Be sure to turn the ignition ON if the fuse or circuit is active only with the ignition on.
Step 4: Observe the Light or LED – If the circuit is complete, the light bulb in the handle of the test light will illuminate.
Based on the test results, you can determine whether there is a problem with the circuit and take appropriate action. If there is no power make sure the test light is grounded properly, also don’t rule out a bad test light bulb. Newer automotive test lights and Power Probes take things further by allowing you to control and back-feed circuits.
An automotive test light is an essential tool for anyone who wants to diagnose and troubleshoot electrical issues in their vehicle. By understanding how an automotive test light works and how to use it, you’ll be able to quickly and accurately diagnose electrical problems in your vehicle and get it back on the road in no time. I hope this quick article sheds some light on this simple, but very effective tool.
Scoot is a Dad, ASE certified mechanic, and blogger. He has been in the automotive business for over 25 Years.