Lighting Systems

Copyright © 2014 Delmar, Cengage Learning

Lighting Systems

Instructor Name: (Your Name)

9CHAPTER


Learning Objectives

• List the various lights used on a truck and indicate the location and color

• Describe why an incandescent light draws more current when first switched on then when the lamp is illuminated at full brilliance

• Explain how the various types of turn signal flashers operate

• Describe the difference between separate stop/turn lamps and combination stop/turn lamps


Learning Objectives (continued)

• Troubleshoot a rear lighting problem on a truck with combination stop/turn lamps

• Troubleshoot a trailer lighting problem• List the advantages and disadvantages of

LED lighting


Exterior Lighting Requirements• FMVSS 108 sets the standards for all

exterior lighting• Marker Lamps – Located on the sides of a

truck or trailer• Identification Lamps – Three centered on

cab and rear of box or trailer. Identification light are sometimes referred to as three bar light.

• Clearance Lights – Located on front a rear top most corners of vehicle


Exterior Lighting Requirements (continued)

• Tail Light – Located on the rear of the truck or trailer

• Parking Lamps – Located the front of the truck

• License Lamp– Located above the rear license plate


Figure 9-3 Truck and trailer lighting locations.

Exterior Lighting Requirements


Incandescent Lamp Ratings• Design Voltage – The rating by which all

other lamp characteristics are measured• Candlepower – Indicate the brightness

of the lamp• Amperage Rating – Indicates the

approximate current draw at the rated voltage

• Power Rating – Listed in watts, it is the amount of heat the lamp will dissipate


Bayonet Type Lamp Base

Figure 9-5 Bayonets on lamp base used to retain lamp in socket and provide ground connection.


Dual Filament Bayonet Type Lamp

Figure 9-7 Dual-filament lamp; two filaments share a common ground.


Wedge-Type Lamp Base

Figure 9-6 Wedge-type lamp base.


Head Lamp Lens

Figure 9-9 Headlamp lens.


Halogen Sealed Beam Lamp

Figure 9-10 Halogen sealed beam.


Head Light Reflector Directs the Light

Figure 9-11 Headlamp reflector directs the light.


Halogen Lamp

Figure 9-12 Halogen lamp.


Composite Headlamp with Interchangeable Halogen Lamp

Figure 9-13 Composite headlamp with replaceable halogen lamp.


Handling Halogen Lamp

Figure 9-14 Handling a halogen lamp.


High Intensity Discharge (HID) Lamp

Figure 9-15 Xenon headlamp components.


WARNING

Never add any extra electrical loads to the headlight circuit, such as driving light. The extra current may lead to headlight circuit failure.


Headlamp Switch in the Park Position

Figure 9-17 Headlamp switch in the part position.


Headlamp Switch in the On Position

Figure 9-18 Headlamp switch in the headlamp ON position.


Floor Mounted Dimmer Switch

Figure 9-19 Floor-mounted dimmer switch.


Flashers• Wired in series with turn signal lamps• Heater element heats when current flows

heating the bimetallic strip causing it to bend• Bimetallic strip bends opening the circuit in

the flasher stopping current flow to lamps• When current flow stops, heater and

bimetallic strip cools closing switch contacts and lighting lamps

• This process repeats itself up to 70 to 110 per minute


Thermal-Type Flasher

Figure 9-20 Thermal-type flasher.


Stop Light Switch• Stop or brake lamps are located at rear of truck• Trucks with air brakes and no tractor protection

valve usually have primary and secondary circuit air pressure stop lamp switches

• Air pressure activated stop lamp switches are normally open and close at approximately 2 to 6 psi (14 to 41 kPa)

• Trucks with tractor protection usually only have one stop lamp switch located at trailer brake air supply circuit


Tech Tip

It is important to note that left and right sides of vehicle always refers to the operators left and right when seated in the drivers seat. This is opposite of left and right when viewed facing the front of the truck.


Turn, Signal, and Stop Lamps

• Combination Stop/Turn – Rear turn signals, hazard lights, and stop lamps all use one single lamp on each side

• Separate Stop/Turn – Amber turn signal lamps that are separate, red stop lamps that are separate


Turn Signal With Stop Light Switch Open and No-Turn Position

Figure 9-22 Turn signal with stop lamp switch open and no-turn position (off).


Stop Lamp Switch Closed, Turn Signal Switch Off

Figure 9-23 Stop lamp switch closed, turn signal switch off, both rear combination lamps illuminate.


Turn Signal Switch in the Left Turn Position

Figure 9-24 Turn signal switch in the left turn position.


Left Turn and Stop Lamp Switch

Figure 9-25 Left turn and stop lamp circuit.


Dual Filament Bulbs and Head Light Switch in Stop Turn Light Circuit

Figure 9-26 Adding headlamp switch and dual-filament lamps to simple turn signal switch.


Open Ground Creates a Series Resistor of Dual Filament Lamp

Figure 9-27 Filaments are in series when dual-filament lamp ground circuit is open.


Current Path for Left Rear Park Light Through the Elements of the Dual

Filament Lamps

Figure 9-28 Path for current flow through left rear lamp stop/turn filament to right rear stop/turn filament with left rear ground open and park lamps on.


Open Ground in Left Hand Rear Combination Lamp Circuit

Figure 9-29 Left rear combination lamp ground open. Park lamps are on, stop lamps are on, and neither left rear filament is illuminated.


Current Path for Left Rear Brake Light Through the Elements of the

Dual Filament Lamps

Figure 9-30 Left rear combination lamp ground is open. Park lamps are off, stop lamps are on, and all running lights illuminate dimly when stop switch is closed.


SAE J560 Trailer Plug

Figure 9-33 SAE J560 trailer electrical receptacle and plug.


SAE J560 Wiring Standards

Figure 9-34 Trailer standard wire insulation colors.


Trailer Socket Connections

Figure 9-36 Trailer socket and trailer cord connector layout looking into the mating ends of the connectors.


Advantages of LEDs

• Longer life expectancy, up to 100,000 hours

• Less heat generated• Less susceptible to shock damage• Fast turn on time• Almost no surge current • Maintain brightness over life of bulb


Disadvantage of LEDs

• Higher initial cost • Prone to theft• May be necessary to scrape snow and ice

from lamps in winter driving conditions due to the fact less heat is generated


LED Construction

Figure 9-40 LED construction; a series resistance is necessary to limit current flow through the LED.


Tech Tip

Luggage compartment lamps are often overlooked in the search of parasitic key-off load currents because there are no windows in the luggage compartment to determine if the luggage lamps are shutting off when the luggage doors are closed.


Instrument Panel Illumination

Figure 9-42 Instrument panel illumination.


Summary• Truck lighting is subject to FMVSS 108 and

CMVSS 108 and other government requirements. It is important to perform lighting repairs so that the truck does not violate the various lighting requirements.

• Incandescent lamps are lamps that contain a thin piece of wire such as tungsten. The sealed glass container does not contain oxygen, which permits the element to glow white hot (incandesce) without being consumed.


Summary (continued)

• Dual filament lamps contain two filaments in one lamp globe. The two filaments share a common ground but have separate voltage sources for each filament. Dual filament lamps are commonly used for turn signals and tail lamps, permitting one lamp to perform two or more functions.


Summary (continued)

• The resistance of an incandescent lamp increases significantly as the element is heated due to current flow. This causes a surge current to flow when the lamp is first illuminated. The surge current of a typical incandescent lamp may be 10 times or more than the current draw with the lamp at operating temperature.


Summary (continued)

• Trucks and trailers may have combination stop/turn lamps or separate stop/turn lamps.

• Trucks with combination stop/turn lamps can exhibit some seemly strange behavior when a ground for a dual filament lamp is open. Other failures such as filaments that are shorted together can also cause problems that seem to be difficult to diagnose.


Summary (continued)• Trailers receive voltage for lighting from the

tractor through a seven way trailer socket. This socket is standardized in North America and other parts of the world.

• Trailer sockets that are green and marked with the abbreviation ABS indicates that the center pin circuit is powered anytime the truck ignition is active. This center pin is used to supply the trailer ABS control module.

• LED lighting has several advantage over incandescent lights, such as long life. Disadvantages of LED lighting include high initial cost.

Documents

Lighting Systems