All vehicles in the United States are required to illuminate the number plate at night, according to the National Highway Traffic Safety Administration. If the headlights and taillights are turned on, the rear number plate also should be lit. Most vehicles are equipped with number plate lights but if one is not mounted on a vehicle, the owner must install it. Failure to comply with vehicle lighting standards could result in a fine.
Purchase a number plate light fixture as well as a light bulb. The PM Lights website states that a variety of number plate lights are available, so one should be chosen that will adequately light the plate and match the car's design or colour. Determine the proper position to mount the number plate light.
Drill a mounting hole on the underside of the mounting area. The PM Lights website explains that the light needs to be mounted on bare metal in order to create an electrical connection. Mount and secure the number plate light onto the back of the vehicle using the screws or bolts that were provided.
The E Trailer website explains that most lighting systems are powered by a direct-current system with two wired ends. A positive and negative terminal is required for the light to work.
Ground the light's electrical connection by making sure that the light is placed on bare metal underneath the mounting location. The E Trailer website explains that the vehicle's chassis is connected to the negative terminal of the battery. Mounting the light on the bare metal provides the grounding that is required for the light to work.
Locate the wire that controls the tail light circuit in order to establish the positive terminal. Connect the wire from the number plate light to the wire from the tail light circuit. The ends of the wires must be spliced in order for them to be connected. Secure the wires together and test the light to make sure that it works correctly.
Carry extra light bulbs so that the light can be repaired in a timely manner.