Lights used for vehicles are classified according to the purpose: for illumination, signaling or informing. For example, headlights are used for illumination to see at night, turn signal lights for signaling to other vehicles or pedestrians, and taillights for informing of the vehicle’s own presence or position.
Besides the general lighting system, vehicles are equipped with systems with various functions depending on the areas or grades.
Lighting systems
(1)Rear light warning system
The burnout of the bulbs for taillights, stop lights, etc., cannot be recognized from the driver’s seat.
The rear light warning system informs the driver about the burnout of the bulbs by a warning light in the combination meter when bulbs such as the taillights or stop lights are burned out.
This system is controlled by the light failure sensor and is mainly installed in the luggage room.
The light failure relay detects the burnout by comparing the voltages when the light is normal and when the circuit opens.
(2)DRL (Daytime Running Light) system
In this system, only the headlights or both headlights and taillights automatically come on while the engine is running even in daytime, so that it can be seen by other vehicles.
Some countries make this system compulsory by law for safety.
The bulb life will be shortened if the light is continuously turned on with the same intensity as that of nighttime. To prevent this, its circuit is so devised that the light intensity is reduced when the DRL system is operating.
(3)Light reminder buzzer system/light auto turn-off system
Headlights and taillights continue to be lit even if the ignition switch is in the LOCK position while the light control switch is ON. The purpose of this system is to prevent the battery from going dead due to the driver forgetting to turn off the headlights or taillights. When the driver’s door is opened with the ignition switch in the LOCK or ACC position or with no key in the ignition key cylinder, the system informs the driver that the lights are still on by a buzzer or automatically turns off the lights.
The system that informs by the buzzer is called the light reminder buzzer system and the system that automatically turns off the headlight is called the light auto turn-off system.
(4)Automatic light control system
When it gets dark and the headlights need to be turned on, usually the driver operates the light control switch.
In this system, when the light control switch is in the AUTO position, the automatic light control sensor detects the level of the ambient light and the system turns on the headlights automatically when it is dark.
The automatic light control sensor is located at the upper portion of the instrument panel.
Some vehicles do not have an AUTO position on the light control switch.
In this case, automatic light control system operates in the OFF position.
(5)Headlight beam level control system
Vehicles slant depending on the load (number of passengers or amount of luggage). That is why the light of the headlights sometimes dazzles drivers of oncoming vehicles.
In this system, operating the headlight beam level control switch adjusts the vertical angle of the headlights.
Some vehicles have an automatic headlight beam level control system that automatically adjusts the headlights to the optimal vertical angle.
(6)Discharge headlight system
Discharge headlight bulbs discharge xenon gas, allowing white light emission and wider distribution of light compared to that of halogen gas.
Longer bulb life is also one of the characteristics of the discharge headlight system.
(7)Illuminated entry system
At night, since the cabin is dark, it is difficult to see the ignition switch or foot area. This system turns on the ignition key illumination or interior lights for a certain period of time after the doors are closed, which makes it easier to insert the ignition key into the cylinder or to see the foot area (only when the interior light is in the DOOR position).
The lighting time varies depending on the models.
(8)Interior light reminder system
Leaving the vehicle with the interior lights on could cause the battery to go dead. To prevent this, this system automatically turns off the interior lights (including the dome light and ignition key cylinder illumination) after a certain period of time elapses with them on and with the door being ajar or open when the ignition switch is in the LOCK position or when the ignition key is not inserted in the ignition key cylinder.
The lighting system consists of the following components.
1.Headlight/discharge headlight (light control ECU for discharge headlight) (front fog light)
2.Rear combination light (rear fog light)
3.Light control and dimmer switch (turn signal switch, front fog/rear fog light switch)
4.Turn signal and hazard warning light
5.Hazard warning switch
6.Turn signal flasher
7.Light failure sensor
8.Integration relay
9.Automatic light control sensor
10.Headlight beam level control switch
11.Headlight beam level control actuator
12.Interior light
13.Door courtesy switch
14.Ignition key illumination