How to Test Fog Light Wires

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 proper way to diagnose the wiring from the vehicle's fog light relay to the lamp assembly itself. This is my fog light here and this is the factory electrical connector from the back of it. I have my test light hooked up to the positive side of my battery and I'm going to take and insert it into the ground side of the circuit. As you can see my test light lights up. That indicates that the circuit has all of its intergrity and you're going to want to take and repeat this step for the other fog light connector which is over here. As you can see that side of the circuit is fine. What you're going to want to do is switch your connector at the battery from the positive side to the ground or negative side of the battery and check the other wire in the connector. As you can see there is two. You're going to want to repeat the procedure. Just switch it from the positive to the negative and select the other terminal. That will check the continuity of both sides. In some cases in order to test the ground side of the circuit, if it happens to have a ground side switch, you will need to turn on the vehicle headlights and engage the fog light switch. What I want you to pay attention to is my test light here. I have it hooked into the ground side of the circuit and hooked up to the ground side of the battery. What I'm going to do is step back to the passenger compartment, turn on the fog light switch and engage the headlights. You'll notice that my test lights will light up. As you can see what I did was turn on the headlights and engaged the fog light switch and the test light lit up. I'm going to go ahead and click the fog light switch on and off a couple of times so you can see how the circuit activates. That's off. My test light should have gone out. I'm going to go ahead and engage the switch again. As you can see the test light lit up. In conclusion for the diagnostic phase of our fog light job, if you perform this last step; engaged the switch and turned on your headlights and your test light does not light up, it indicates that there is a broken wire between your connector and your switch. If your test light does light up, that means that the problem is between the connector and the lamp indicating that your lamp has failed and needs replaced. "