As vehicles progressed from the engine powered wagon to today’s modern autonomous and electric vehicles so have the mechanics that repair them. Repair procedures have become more complicated and require computerized equipment to sometimes complete the simplest of repairs.
While these repairs have gotten more complicated when it comes to electric diagnosis, the tools that we have used for years are still around completing diagnosis on the most complicated repairs.
I myself have diagnosed high voltage electrical systems with the best test light in my tool box that is probably, at this point, over 15 years old. And let’s be honest, it really is just a light bulb with a test lead.
The most important electrical diagnostic tools in any person’s tool box at this point is a; multimeter and a test light.
So, how do we use these tools and what tests can each perform? Let’s jump in and find out.
Table of Contents
Testing With A Test Light
A test light is basically a light bulb that has a ground clamp and a test probe. This light bulb can do some very useful testing, some testing that isn’t even possible with more advanced tools like a multimeter.
The most common use of a test light is to check for power at a circuit. After clamping the ground lead to the ground terminal on the battery, the test light can probe various parts of a circuit.
If there is voltage present on these various parts of the circuit the light bulb will illuminate.
The other useful thing you can do with a test light is to “load” test a wire. A light bulb is considered a load and requires current to light up the bulb. By using a test light and monitoring if the test light illuminates, a mechanic can confirm if the wiring is capable of handling the current flow required in the circuit.
As you can see, there are some unique tests that a test light is capable of doing. But sometimes you need to complete electrical tests that only a multimeter can perform.
Testing With A Multimeter
While a test light is a very simple tool, a multimeter is more advanced and is capable of completing many different tests that a test light cannot. Sometimes because of this, an automotive multimeter is the best tool for the job.
The multimeter that you have will be the limitation of the tests that you will be able to perform.
A low price multimeter for example, will be capable of testing voltage, resistance, and amperage. These are the most common measurements that are tested in an automotive diagnostic situation.
However there are certain times when you need more tests to find the root cause of the problem. For example, a quick voltage spike may not be seen when watching the multimeter. In this situation a min/max record feature will allow you the ability to see very fast changes in a circuit that the human eye cannot pick up.
This is only one of the many extra features. The most capable of automotive multimeters is the Fluke 88V. Among basic features like voltage, resistance and amperage tests this meter is also capable of diode testing, capacitor tests, temperature and will even auto range the display depending on the test results.
Which Test Tool Do I Need?
As you can see, both tools have advantages. It can be a difficult decision when trying to decide which electrical test tool will be best for your tool box.
I will suggest this, it never hurts to own them both. Personally I own an old, trusty test light and three different styles of multimeters.
Yes, I may have a tool buying problem. Just dont tell my wife.
These tools have always allowed me to get the job done in a timely manner and always the correct diagnosis.
John Morris is an automotive professional with over 20 years of experience in the automotive industry. Currently he is spreading his automotive opinions at autoknowit.com
