The side and tail lights, however, which you may need to leave on when the car is parked, are always wired independently of the ignition switch. When fitting extra accessories, such as a rear window heater which consumes a heavy current, always wire it through the ignition switch.
The fuse box is often located in a cluster of components, as illustrated here. The box is shown with the cover off.
When an electrical component stops working the fault may be in the component, in the electrical circuit or in the fuse that protects them. Because the fuse is a likely cause, and the easiest to check, look at it first.
Current flows along a single cable from the battery to the component being powered, and back to the battery through the car metal body. The body is connected to the earth terminal of the battery by a thick cable.