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Lighting and Wiring Fundamentals

Chapter 32

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Objectives• Describe differences between wire and cable• Explain the fundamentals of operation of

automotive lighting and wiring• List when different circuit protection devices

would be used

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Introduction• Lights and wiring:

– Can be a complicated system• Electricity is provided through:

– Wiring – Cables– Fibers

• Circuit protection devices:– Fuses– Circuit breakers– Fusible links

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Wire and Cable• Chemicals, corrosion, vibration, and heat

– Damage wiring• Primary and secondary wires

– Primary wiring: low-voltage wiring– Secondary wiring: ignition wiring– American Wire Gauge (AWG): describes the size

of wire or cable used– Cables: large wires that allow more electrical

current to flow

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Circuit Protection Devices• Fuse: protective device designed to melt when

the flow of current becomes to high– Replaceable fuses

• Blade type• Ceramic type• Glass tube cartridge type

– Fuse link • Length of wire smaller in diameter than the wire it

is connected to

© © 2012 Delmar, Cengage Learning

© © 2012 Delmar, Cengage Learning

Circuit Protection Devices (cont'd.)

• Circuit breakers– Used in automobiles: usually self-resetting

• Breaker “trips” and then resets– Bimetal strip: two metal strips with different

expansion rates• Higher expansion metal will become longer and

will break the switch contact• Contact is reestablished when it cools

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Lighting• Light bulbs

– Often called lamps– Electricity flows through filaments– Filament provides a resistance to electron flow

• It heats up and glows, causing light

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Headlamps• Headlight and headlamp

– Terms are used interchangeably– Intensity of a headlamp: rated in candlepower

• Sealed-beam headlamp construction– Have an inner glass or plastic reflector surface

• Type I lamp: high beam only• Type II lamp: both low and high beams

• Halogen lamps – Produce a 25% higher output of “whiter” light– Conventional sealed beam or composite

© © 2012 Delmar, Cengage Learning

© © 2012 Delmar, Cengage Learning

Headlamps (cont'd.)• High-intensity discharge lamps

– Provide three times more light than conventional halogen headlamps

• Adaptive headlights – Can swivel up to 15 degrees right or left

• Headlight switch– Multifunction on steering column or mounted on

dash panel– Typically two or three positions besides the off

position

© © 2012 Delmar, Cengage Learning

© © 2012 Delmar, Cengage Learning

Headlamps (cont'd.)• Dimmer switch

– Changes headlights from low to high beam• Automatic headlight dimmer

– Detects oncoming cars• Courtesy lights

– Interior dome and underdash lights• Headlight wiring

– Many use grounded electrical systems– Daytime running lights: powered when engine is

running

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Headlamps (cont'd.)• Automatic headlights

– Use a light-sensitive photocell sensor– Delay shutoff keeps lights on for a short period

• Flash to pass– Raising turn signal activates high beams

• Driving lights and fog lamps – Occasionally installed as original equipment– Normal lights do not work well in fog

• Fog reflects light back at the driver

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Taillights• Taillight bulbs

– Come in many sizes and types– Are usually ground through the base to the bulb

socket• Light socket: usually grounded to frame

• Newer vehicles– Bulbs have a plastic socket mounted in plastic

housings

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Light Bulb Identification • Miniature lights: bulbs smaller than headlamps

– Correct replacement bulb must be used• Otherwise, circuit problems could result

• Bulbs are numbered by the ANSI– Identification number is the bulb trade number

• Stoplight switch– Activated by a mechanical switch on brake pedal

• Taillights and brake lights– Taillight bulbs have one or two filaments

• Activated by brakes

© © 2012 Delmar, Cengage Learning

© © 2012 Delmar, Cengage Learning

Fiber Optics• Light can be transmitted through a special plastic

called polymethacrylate– Fiber-optic strands illuminate indicator on fender

• LED and neon lights – Energy efficient, long lasting, and compact

• Center high-mount stop lamps– Row of LEDs, filament bulb, or a neon tube

• Adaptive brake lights – Intensity increases as driver pushes on brake

pedal

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Turn Signals• Turn signal circuit components

– Switch– Signal flasher– Two indicator bulbs – Stoplight filaments or rear stoplight bulbs– Two bulbs in the front of the vehicle

• Turn signal – Usually part of a multifunction switch in the

steering column

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Signal Flasher Operation• Turn signal flashers

– Turn signals and safety hazards– Mechanical or automatic

• Electronic turn signal flashers – Operate when a transistor is triggered on and off

• Transistor: electronic switch with no moving parts– Operate turn signals and hazard warning lights

• Relay turn signals– Mechanical – Electronic

© © 2012 Delmar, Cengage Learning

© © 2012 Delmar, Cengage Learning

Hazard Flashers• Required on cars manufactured after 1967

– Circuit is powered directly from the battery• Emergency flasher switch locations

– Side of the steering column – Dash panel– Glove box

• Emergency warning systems – Use a variable load flasher

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Back-Up Lights• Operation

– Key is on – Transmission selector is moved to R position– Lights at the rear of the vehicle are illuminated

• Provide a white light that allows a driver to see – Provides a warning to other drivers

• Some vehicles use the same fuse for turn signals and back-up lights– Current is supplied from the fuse panel to the

back-up light switch

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Wipers and Horn• Windshield wiper motor

– Wiper circuit has fuse or circuit breaker and wiper switch

– Electromagnetic wiper motors: two brushes on armature

– Typical permanent magnet motor: three brushes• Intermittent wipers

– Allow variations in the time interval• Rain-sensing: begin automatically when water

sensed • Speed-sensitive: controlled with sensor input

© © 2012 Delmar, Cengage Learning

© © 2012 Delmar, Cengage Learning

Wipers and Horn (cont'd.)• Windshield washer

– Components• Reservoir • Switch and pump• Washer nozzles• Hoses and connections

• Types and features– Rear window wiper-washer– Headlight wiper-washers– Windshield washer low-fluid indicator

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Wipers and Horn (cont'd.)• Horn circuit components

– Horn– Fuse and wiring– Horn switch– Relay

• Dashboard is called an instrument panel– Combined analog and digital displays

• Electric gauges – Thermal/bimetal gauges, magnetic gauges, and

digital panel gauges

© © 2012 Delmar, Cengage Learning

© © 2012 Delmar, Cengage Learning

Miscellaneous Gauges• Several gauges are on the instrument panel

– Speedometer/odometer– Tachometer– Engine coolant temperature gauge– Engine oil pressure gauge– Fuel level gauge– Lamp-out warning light– Other warning lights– Other electrical accessories

© © 2012 Delmar, Cengage Learning