Sooner or later your car is likely to have light problems. It could be caused by bad light bulbs, fuses, switches, relays, battery , or simply loose or shorted wires. The light problem might be that one side is on and the other side is off. It could be that lights are always on or won’t turn on at all. Or they could be flickering. This video discusses ways to test and eliminate possibilities so that you can quickly focus on the real faulty components.
How to troubleshoot car light problems, such as lights not turning off or one-on one-off