2. The Basic Bulb Bulb uses electrical current to produce light.
Filament
Support 1
Support 2
Glass
Bulb uses electrical current to produce light.
Filament held in position by supports.
One support connects to centre contact.
One support connects to cap.
Cap
Air removed to reduce heat loss, oxidation and vaporization.
Centre contact
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3. The Basic Bulb Filament is heated by current flow and produces light.
Centre contact
Support 1
Support 2
Cap
Glass
Filament is heated by current flow and produces light.
Emits white light when heated to 2300°C.
Bulb produces less light when supply voltage is below bulb rating.
Bulb produces more light when supply voltage is above bulb rating, until filament burns away.
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4. Bulb Types Quartz halogen type.
Halogen bulb
Quartz halogen type.
Voltage terminals
Metal flange with lugs
Used in headlights, spot, driving and fog lights.
Quartz
Quartz used instead of glass, due to strength and high temperature properties.
End shield
Shield
Interior is pressurized to reduce burning away of filaments.
Main filament
Dip filament
Shields allow bulb to produce required beam patterns.
Lugs on metal flange ensure bulb is fitted correctly.
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5. Bulb Types Small bayonet cap, single contact type.
Used in side, rear, license plate, fog and indicator lights.
Small bayonet cap, twin contact type.
Used in combined brake and rear lamps.
Xenon HID bulbs, used in headlights.
Produce more light than halogen bulbs and use less power.
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6. A Basic Headlight Contains a bulb, a parabolic reflector and a lens.
May be fitted with a shield to cut-off light.
Voltage terminals
Voltage terminals at rear.
Shield
Headlight is weatherproof.
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7. Basic Headlight Beam Patterns
Parabolic reflector
Shape of reflector determines beam pattern.
Filament at focal point
Parallel beam
Bulb
Parallel beam produced by positioning filament at focal point.
Ideal design for spot lights.
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8. Basic Headlight Beam Patterns
Filament above focal point
Dip
beam
Parabolic reflector
Bulb
Dip beam produced by positioning filament above focal point.
Side beam produced by positioning filament to one side of reflector.
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9. Basic Headlight Beam Patterns
Some bulbs are fitted with shields.
Concentrated dip beam
A shield under a filament concentrates the beam pattern upward.
Shield
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10. Free Form Headlights Reflectors are designed to tight tolerances.
Reflector segments
Reflector
Shield
Filament
Front
view
Side
Surface focuses and scatters light beams.
Dip beam pattern
Divided into segments to illuminate segments of road.
All of the surface area is used to provide a beam pattern.
Lens is a clear cover, with no optical pattern.
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11. Projection Headlights
Small in diameter, but produce high output.
An ellipsoidal reflector reflects light onto a lens.
Lens
Ellipsoidal reflector
Filament
Beam pattern
The lens projects light in the required pattern.
Shield cuts-off unwanted light.
Shield
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12. Flasher Unit Indicator flash rate must be constant.
Produced by a device known as a flasher unit.
Usually contained in relay / fuse box, under the dashboard.
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13. Flasher Unit - Bimetal Type
Bimetal strip and heating element.
12V in, from indicator switch
To indicator lights
Bimetal strip
Contacts
Heating element
Turn signal switch set to on, current flows through heating element, warming bimetal strip.
Bimetal strip bends, contacts open, lights off.
While contacts are open, heating element and bimetal strip cool down.
Bimetal strip returns to original position, contacts close, lights on.
Process repeats until turn signal switch is set to off.
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14. Flasher Unit - Electronic Type
Main components:
Integrated circuit
Relay
Capacitor
Resistor
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15. Hazard Warning Lights Warn of a possible emergency or hazard.
International
warning triangle
Red hazard
warning button
Activated by red push button.
Usually mounted on steering column.
When pushed down, all indicator (hazard) lights flash.
Button marked with international warning triangle.
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16. Indicator/Hazard Warning Schematic
Ignition
switch
Hazard switch
Indicator
flasher unit
Indicator switch
Indicator lights
Battery
Indicator operation: flasher unit receives power via fuse, ignition switch and normally closed hazard switch contact.
Hazard operation: flasher unit receives power direct from battery, via fuse and hazard switch contacts.
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