How do you tell if your tail light fuse is blown?

When an electrical circuit in a car fails, the most likely reason is a blown fuse. The owner's manual will contain a diagram of the different fuses, each circuit identified. Identifying the possible fuse, from the manual, and then looking at the fuses physically, will most likely show which fuse is involved. There is also likely, a fuse diagram within the fuse box showing where each fuse is. The fuse needs to be visually inspected. Good fuses will show a shiny metal link on top. Blown fuses will show a dark gap. Sometimes, you need to pull the fuse out of the socket and look at it through the light. You can then see the broken link clearly. Another method of finding blown fuses is by using a volt meter. Normally, the voltage across a fuse is trivial, but when a fuse has blown, the voltage across it will be around 13 volts. This is because the circuit has been broken and the full battery voltage is across it. For a tail light, the lights need to be turned on when checking the voltage across the fuse.