How to Use a Test Light on Your Car

Video Transcript

"Hi, my name is Nate McCullough on behalf of Expert Village. In these clips we're going to talk about the proper way to diagnose and replace your vehicle's fog lights or accessory lights. In this clip I'm going to talk about the principle of how a test light works and go ahead and test the switch inside the vehicle. A test light pretty much checks the continuity or the connectivity of any given electrical circuit. What I'm going to do now is hook this up to a ground on the battery. I'm going to put it right there and I'm going to connect it to the positive on the battery. As you can see my light lights up. What that does is it tests the continually of my test light itself. To apply this to the vehicle, what you would see is I would take my ground off and pick a ground on the engine. You want to just pick a bolt right about there. Once I'm grounded, we'll go ahead and check the positive on the battery. As you can see we're not connected to anything else on the battery but the positive. What this does is test the grounding circuit for the vehicle. The other circuit that you want to check is the positive. What we'll do from there is we'll hook it to the ground and find ourselves a good positive connection. I have a remote fuse location here. I'm going to go ahead and touch that connection, you can see my light lights up. That will check the continually of any circuit be either positive or ground. We're going to use these principles to diagnose our switch, our wiring and our fog lights themselves. "