The tail lights of the Nissan Xterra are designed to be simple enough to turned on with a simple switch, but it is actually a bit more complicated of a device. This is why whenever the tail lights malfunction, it can be due to a variety of different reasons. And knowing how to diagnose which of these causes might have lead to the failure of the tail lights will not only help you save money on repair and replacement costs, it also give you a better understanding of how your car works as well. The following are some of the common signs of Nissan Xterra tail light failure and how to diagnose them.
If one of the tail lights isn't lighting up when the brake pedal is stepped on, it may be due to a burned out bulb. Remove the housing and detach the bulb from its socket. Check the condition of the filament; if it is severed and there is black powder on the inner side of the glass, the bulb needs replacing. However, if the bulb appears to be in good condition, check the socket for rust. Severely corroded sockets may not allow enough voltage to reach the bulb and need to be replaced.
On the other hand, if both of the tails have stopped working, the problem may be with a busted fuse. The tail lights are protected from short circuit and overloading by a small fuse, and in the event of an electrical surge it will absorb most of the energy at the expense of being burned out in the process. Look for the fuse in the fuse box (for Nissan Xterras, it is located under the instrument panel on the left of the dashboard) and pull it out carefully. Check if the metal strip inside the fuse is still in one piece. If the strip is broken, the fuse is busted and must be replaced. However, if the wire appears to be in good condition, the problem might be with loose or damaged wiring.
Fluctuating tail light brightness may indicate a problem with the vehicle's alternator. Connect a voltmeter to the car battery and check the display. If the displays anything less than 1.3 volts, the alternator is malfunctioning.