Park/Tail/Marker/License Lights

Park, tail, and marker lights are all low-intensity or low-wattage bulbs used to mark the outline or width of the vehicle. Park and tail lamps tend to be installed close to the corners of the vehicle. Park lamps are placed to the front of the vehicle, or in some cases they are incorporated in the headlight assembly and are white or yellow in color. Tail lamps are red and usually installed in a cluster assembly with the stops lamps at the rear of the vehicle.

License plate lamps produce a white light and are designed to illuminate the lettering on the license plate at night without the white light itself being seen from the rear. The bulbs are connected in parallel to each other so that the failure of one filament will not cause a total circuit failure. A license plate illumination lamp or lamps are usually connected in parallel to the taillights and operate whenever the taillights are on.

Taillights are usually incorporated in a cluster assembly at the rear of the vehicle. Government regulations control the height of the lamps and their brightness.

Park lights are located at the front of the vehicle and are used at night when the vehicle is parked on the side of the road and are also on anytime the headlights are on. They use low-wattage bulbs and may have a lens or diffuser that makes the emitted light widespread. In some cases, park lights are incorporated in the headlight assembly. Park lights operate when the light switch is moved to the park light position. For safety reasons, park lights and taillights continue to operate when the light switch is moved to the headlight position. The bulbs are connected in parallel with each other.

On computer-controlled lighting systems, the park lights and taillights are BCM controlled. The lights are supplied with power and ground through a networked light controller. The controller is connected to a network/bus system (discussed later in this chapter) by the twisted pair of communication wires. The park light switch is hardwired to a module. When the park light switch is activated, the module sends a park light request out on the network where the appropriate controllers pick up the message and supply power or ground to the appropriate light bulb filaments to illuminate the park lights.

FIGURE 39-13
Marker lights on an SUV.

Marker lights are used to mark the sides of some vehicles are often located down the sides of the vehicle or trailer. They can be located on the front and rear fenders. On newer vehicles, they are sometimes placed on side-view mirrors, or between the front and the rear doors on large SUVs or pick-ups Figure 39-13. Red marker lamps face toward the rear, and yellow lamps face toward the front of the vehicle. These lights are designed to work when the park lights or headlights are selected and sometimes operate as turn signals so a driver can warn others of his or her intent to switch lanes or turn a corner.

Government regulations control the positioning of lights, including the height of the lamps’ beam and their brightness. The park, tail, marker, and license plate lamps operate when the headlight switch is in both the park and the headlight-on positions. The bulbs are connected in parallel to each other so that the failure of one filament will not cause a total circuit failure. Tail and park lamps may use separate fuses, so if one circuit fails the other will continue to operate.

Technician Tip
In many vehicles produced before the mid-1960s, front park lights turn off when the headlights are on. The thinking was that if the headlights are on, then the park lights were unnecessary. The problem arose when a headlight failed and only one light illuminated on the front of the vehicle, mimicking a motorcycle, which gave the impression of the vehicle being narrower than it is. Designing the park lights to stay on with the headlights helped to prevent this unsafe situation.