Automotive
Lighting Systems
The power to both the interior and exterior lights is provided by the lighting
system. It consists of the headlights, parking lights, tail-lights, marker lights, instrument
illumination or dash lights, courtesy lights, dome/map lights, headlight switch, and various
other control Switches. Some vehicles also use other lights such as vanity mirror light, the
glove box light, the underhood light, and the trunk light and they are also part of the
lighting system. Lights such as hazard warning, turn signal, backup, and stop are not usually
found in the main lighting system. They are found in only some vehicles and are operated by a
separate control circuits.
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- A lamp generates light as electricity flow through the filament. These lamps get very hot. The changing
of electrical energy to heat energy in the filament is so strong that the filament actually starts to glow
and emits light.
- Lamps are normally one of two types: a single filament or a double filament.
- Double filament bulbs are designed to serve more than one functions. They can be used as a single bulb
in the taillight circuit, stop light circuit, and the turn signal circuit.
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HEADLIGHTS
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Headlight design and construction has over the years been influenced by the changes in technology.
In the past cars had two or four round headlights called sealed-beam headlights. Headlights today
are an integral part of a vehicles overall design. On today's vehicles the headlights are based on
sealed-beam, composite, or high intensity discharge
lamps.
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Sealed-Beam Headlights
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- Today, some vehicles use sealed-beam headlight that are the halogen type.
The bulb, filled with iodine vapor, is make of made of high-temperature-resistant glass
and it surrounds a tungsten filament. The halogen-filled inner bulb is then installed
in a sealed glass or plastic housing.
- With the halogen added to the inner bulb, the tungsten filament is capable of
withstanding higher temperatures that of standard sealed-lamps.
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Composite Headlights
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The most common headlight system used today is the halogen type that use a replaceable bulb.
These system are called composite Headlights.
- By using composite headlight system manufactures are able to produce many different style of headlight
lens. This allows for improvements in the aerodynamics, fuel economy, and styling of the vehicle.
- High-intensity discharge or HID headlamps use gas-discharge lamps and are electronically
controlled. Because the light's spectrum is much closer to daylight than that of a halogen bulb, they
are recognizable by a blue-white color.
- Instead of using filament, an electrical arc is created between two electrodes that excite a
gas(usually xenon)inside the headlamp, which in turn vaporizes metallic salts that
sustains the arc and emit light. The presence of an inert gases amplifies the light given of by the
arcing.
- Xenon high-intensity-discharge headlights employ xenon gas to produce a slightly bluish light, up to
three times brighter than halogen headlights. Technically a high-intensity-discharge (HID) light, xenon
headlights are named for the inert gas they employ to amplify light produced by electricity jumping between
two electrodes. HID lights don’t use a filament, as do incandescent headlights, and they tend to last two
to three times longer. They also provide much more uniform intensity. Aim a set of xenon headlights at a
wall, and you’ll see they define a sharp line at the top of the projected light pattern rather than the
gradual fade common to conventional headlights. HID lights produce ultraviolet as well as visible light,
which makes reflective highway signs glow more brilliantly.
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Headlights switches are either mounted on the dash panel or are part of a multifunctional switch on
the steering column. The headlight switch controls most of the vehicle's lighting systems.
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Some vehicle's come equipped with automatic on headlights. They are controlled by a light-sensitve
photo cell senor/amplifier and a hedlight contro relay.
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In normal operation, the photocell sensor/amplifier, which is usually monted uner a group of
perforated holes in the upper instement panel pad or slotted holes in the defroster grelle panel,
is exposed to ambient, light. As the level decreaes, the light sensors resistance increases. When
the resistance increaces to a preset amount, headlights,exteriorlights, and instrument illumination
light turn on. The lights remain on until the system is turned off or the ambient light level
increases.
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Their is, in most automatic light systems a headlamp delay system as well. This system allows the
headlights to stay on for a short period of time after the ignition switch is turn off.
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The dimmer switch is provied so the driver can switch between high an low beams. A dimmer switch is
connected in headlight circuit and control's the electricity's path to the headlights. The
high-beam headlights are wired separately from the low-beam lamps. Though the dimmer switch was for
many years on the floor and foot activated, newer vehicles have the dimmer switch on the steering
column which increases driver accessibility.
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Interior Lights
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Engine Compartment Light
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- When the hood of the vehicle open a light mercury switch is closed and light thethe
underhood area.
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Glove Box light
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- When the glove box door is opened it closes the glove box light switch conacts and the
light comes on.
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Luggage Comprtment Light
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- Mounted on the underside of the trunk lid, it comes on when you open the trunk
lid.
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Vanity Light
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- On the back of the sun visor. Generally has a manual switch to turn it on.
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Courtesy Lights
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- There are an number of differient types of courtesy lights, depending on the vehicle. They
are used to light the entire interior of the vechicle.
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Rear Exterior Lights
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Tail Lights
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Brake Lights (stop)
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Turn Signal Lights
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Hazard Warning Lights
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Backup Lights
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