Two Troubleshooting Tips for your Audi A4 Fog Light
Just like any automotive lighting, your Audi A4's fog light is prone to damage-both internally and externally. You might be surprised to realize that your fog lights are not working at the time you need them the most. A blown fuse, a busted bulb, or a faulty switch or wiring could be the cause of this problem, but you're not really sure because something like that never happened before. Before you hit the road again, equip yourself with these simple tips on how to troubleshoot your Audi A4's fog light:
Fog lights are out.
If you're sure that the fog light bulbs are not causing this problem, you can test the flow of electricity to and from the fuse. To do this, you will need a voltmeter. Simply look for a bare metal, screw, or bolt near the fuse box of your car. Place the tip of the voltmeter's black wire to the metal part, and then place the tip of its red wire on the top end of the fuse. If you get a reading, then there is no problem with the electrical connection and the fuse. But if there's no reading, then there is a problem with a wiring on the fuse and the battery that needs to be checked or replaced. You can also check the fog light switch using the voltmeter, and follow the same method until you figure out what is causing the problem.
Fog lights won't turn off.
If your fog lights won't turn off, even if the ignition is already turned off and the battery is dead, then the problem could be caused by a defective fog light switch. You can use your trusty voltmeter to check the wirings of the switch and the switch itself. With the switch turned on, set the tip of the end of voltmeter's red wire to the "out" terminal of the switch. If you don't get a reading, then you are correct that the problem is caused by a faulty switch. You need to replace it immediately to get your fog lights back in proper working order.