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Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
Halderman ch056 lecture
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Halderman ch056 lecture

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  • Figure 56-1 Dual-filament (double-contact) bulbs contain both a low-intensity filament for taillights or parking lights and a high-intensity filament for brake lights and turn signals. Bulbs come in a variety of shapes and sizes. The numbers shown are the trade numbers.
  • Chart 56-1 Bulbs that have the same trade number have the same operating voltage and wattage. The NA means that the bulb uses a natural amber glass ampoule with clear turn signal lenses.
  • Chart 56-1 (continued) Bulbs that have the same trade number have the same operating voltage and wattage. The NA means that the bulb uses a natural amber glass ampoule with clear turn signal lenses.
  • Figure 56-2 Bulbs that have the same trade number have the same operating voltage and wattage. The NA means that the bulb uses a natural amber glass ampoule with clear turn signal lenses.
  • Figure 56-3 Close-up a 2057 dual-filament (double-contact) bulb that failed. Notice that the top filament broke from its mounting and melted onto the lower filament. This bulb caused the dash lights to come on whenever the brakes were applied.
  • Figure 56-4 Corrosion caused the two terminals of this dual-filament bulb to be electrically connected.
  • Figure 56-5 Often the best diagnosis is a thorough visual inspection. This bulb was found to be filled with water, which caused weird problems.
  • Figure 56-6 This single-filament bulb is being tested with a digital multimeter set to read resistance in ohms. The reading of 1.1 ohms is the resistance of the bulb when cold. As soon as current flows through the filament, the resistance increases about 10 times. It is the initial surge of current flowing through the filament when the bulb is cool that causes many bulbs to fail in cold weather as a result of the reduced resistance. As the temperature increases, the resistance increases.
  • Figure 56-7 Typical brake light and taillight circuit showing the brake switch and all of the related circuit components.
  • Figure 56-9 The typical turn signal switch includes various springs and cams to control the switch and to cause the switch to cancel after a turn has been completed.
  • Figure 56-10 When the stop lamps and turn signals share a common bulb filament, stop light current flows through the turn signal switch.
  • Figure 56-11 When a right turn in signaled, the turn signal switch contacts send flasher current to the right-hand filament and brake switch current to the left-hand filament.
  • Figure 56-12 Two styles of two-prong flasher units.
  • Figure 56-13 A hazard warning flasher uses a parallel resistor across the contacts to provide a constant flashing rate regardless of the number of bulbs used in the circuit.
  • Figure 56-14 The side-marker light goes out whenever there is voltage at both points X and Y. These opposing voltages stop current flow through the side-marker light. The left turn light and left park light are actually the same bulb (usually 2057) and are shown separately to help explain how the side-marker light works on many vehicles.
  • Figure 56-15 Typical headlight circuit diagram. Note that the headlight switch is represented by a dotted outline indicating that other circuits (such as dash lights) also operate from the switch.
  • Figure 56-16 A typical four-headlight system using sealed beam headlights.
  • Figure 56-17 A typical composite headlamp assembly. The lens, housing, and bulb sockets are usually included as a complete assembly.
  • Figure 56-19 The igniter contains the ballast and transformer needed to provide high-voltage pulses to the arc tube bulb.
  • Figure 56-20 HID (xenon) headlights emit a whiter light than halogen headlights and usually look blue compared to halogen bulbs.
  • Figure 56-21 LED headlights usually require multiple units to provide the needed light as seen on this Lexus LS600h.
  • Figure 56-22 Typical headlight aiming diagram as found in service information.
  • Figure 56-23 Many composite headlights have a built-in bubble level to make aiming easy and accurate.
  • Figure 56-24 Adaptive front lighting systems rotate the low-beam headlight in the direction of travel.
  • Figure 56-25 A typical adaptive front lighting system uses two motors: one for the up and down movement and the other for rotating the low-beam headlight to the left and right.
  • Figure 56-26 Typical dash-mounted switch that allows the driver to disable the front lighting system.
  • Figure 56-27 Typical daytime running light (DRL) circuit. Follow the arrows from the DRL module through both headlights. Notice that the left and right headlights are connected in series, resulting in increased resistance, less current flow, and dimmer than normal lighting. When the normal headlights are turned on, both headlights receive full battery voltage, with the left headlight grounding through the DRL module.
  • Figure 56-28 Most vehicles use positive switching of the high- and low-beam headlights. Notice that both filaments share the same ground connection. Some vehicles use negative switching and place the dimmer switch between the filaments and the ground.
  • Figure 56-29 A typical courtesy light doorjamb switch. Newer vehicles use the door switch as an input to the vehicle computer and the computer turns the interior lights on or off. By placing the lights under the control of the computer, the vehicle engineers have the opportunity to delay the lights after the door is closed and to shut them off after a period of time to avoid draining the battery.
  • Figure 56-30 An automatic dimming mirror compares the amount of light toward the front of the vehicle to the rear of the vehicle and allies a voltage to cause the gel to darken the mirror.
  • TAILLIGHT BULB REPLACEMENT 1 The driver noticed that the taillight fault indicator (icon) on the dash was on any time the lights were on.
  • TAILLIGHT BULB REPLACEMENT 1 The driver noticed that the taillight fault indicator (icon) on the dash was on any time the lights were on.
  • TAILLIGHT BULB REPLACEMENT 1 The driver noticed that the taillight fault indicator (icon) on the dash was on any time the lights were on.
  • TAILLIGHT BULB REPLACEMENT 1 The driver noticed that the taillight fault indicator (icon) on the dash was on any time the lights were on.
  • TAILLIGHT BULB REPLACEMENT 2 A visual inspection at the rear of the vehicle indicated that the right rear taillight bulb did not light. Removing a few screws from the plastic cover revealed the taillight assembly.
  • TAILLIGHT BULB REPLACEMENT 3 The bulb socket is removed from the taillight assembly by gently twisting the base of the bulb counterclockwise.
  • TAILLIGHT BULB REPLACEMENT 4 The bulb is removed from the socket by gently grasping the bulb and pulling the bulb straight out of the socket. Many bulbs required that you rotate the bulb 90° (1/4 turn) to release the retaining bulbs.
  • TAILLIGHT BULB REPLACEMENT 5 The new 7443 replacement bulb is being checked with an ohmmeter to be sure that it is okay before it is installed in the vehicle.
  • TAILLIGHT BULB REPLACEMENT 6 The replacement bulb in inserted into the taillight socket and the lights are turned on to verify proper operation before putting the components back together.
  • OPTICAL HEADLIGHT AIMING 1 Before checking the vehicle for headlight aim, be sure that all the tires are at the correct inflation pressure, and that the suspension is in good working condition.
  • OPTICAL HEADLIGHT AIMING 2 The headlight aim equipment will have to be adjusted for the slope of the floor in the service bay. Start the process by turning on the laser light generator on the side of the aimer body.
  • OPTICAL HEADLIGHT AIMING 3 Place a yardstick or measuring tape vertically in front of the center of the front wheel, noting the height of the laser beam.
  • OPTICAL HEADLIGHT AIMING 4 Move the yardstick to the center of the rear wheel and measure the height of the laser beam at this point. The height at the front and rear wheels should be the same.
  • OPTICAL HEADLIGHT AIMING 5 If the laser beam height measurements are not the same, the floor slope of the aiming equipment must be adjusted. Turn the floor slope knob until the measurements are equal.
  • OPTICAL HEADLIGHT AIMING 6 Place the aimer in front of the headlight to be checked, at a distance of 10 to 14 inches (25 to 35 cm). Use the aiming pointer to adjust the height of the aimer to the middle of the headlight.
  • OPTICAL HEADLIGHT AIMING 7 Align the aimer horizontally, using the pointer to place the aimer at the center of the headlight.
  • OPTICAL HEADLIGHT AIMING 8 Lateral alignment (aligning the body of the aimer with the body of the vehicle) is done by looking through the upper visor. The line in the upper visor is aligned with symmetrical points on the vehicle body.
  • OPTICAL HEADLIGHT AIMING 9 Turn on the vehicle headlights, being sure to select the 9 correct beam position for the headlight to be aimed.
  • OPTICAL HEADLIGHT AIMING 10 View the light beam through the aimer window. The position of the light pattern will be different for high and low beams.
  • OPTICAL HEADLIGHT AIMING 11 If the first headlight is aimed adequately, move the aimer to the headlight on the opposite side of the vehicle. Follow the previous steps to position the aimer accurately.
  • OPTICAL HEADLIGHT AIMING 12 If adjustment is required, move the headlight adjusting screws using a special tool or a 1/4-in. drive ratchet/socket combination. Watch the light beam through the aimer window to verify the adjustment.
  • Transcript

    • 1. LIGHTING AND SIGNALING CIRCUITS 56
    • 2. Objectives <ul><li>The student should be able to: </li></ul><ul><ul><li>Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “E” (Lighting System Diagnosis and Repair). </li></ul></ul><ul><ul><li>Read and interpret a bulb chart. </li></ul></ul><ul><ul><li>Describe how interior and exterior lighting systems work. </li></ul></ul>
    • 3. Objectives <ul><li>The student should be able to: </li></ul><ul><ul><li>Read and interpret a bulb chart. </li></ul></ul><ul><ul><li>Discuss troubleshooting procedures for lighting and signaling circuits. </li></ul></ul>
    • 4. INTRODUCTION
    • 5. Introduction <ul><li>The major light-related circuits and systems covered include: </li></ul><ul><ul><li>Exterior lighting. </li></ul></ul><ul><ul><li>Headlights (halogen, HID, and LED). </li></ul></ul><ul><ul><li>Bulb trade numbers. </li></ul></ul><ul><ul><li>Brake lights. </li></ul></ul><ul><ul><li>Turn signals and flasher units. </li></ul></ul><ul><ul><li>Courtesy lights. </li></ul></ul><ul><ul><li>Light-dimming rearview mirrors. </li></ul></ul>
    • 6. EXTERIOR LIGHTING
    • 7. Exterior Lighting <ul><li>Headlight Switch Control </li></ul><ul><ul><li>Headlight switch controls the following lights: </li></ul></ul><ul><ul><ul><li>Headlights </li></ul></ul></ul><ul><ul><ul><li>Taillights </li></ul></ul></ul>
    • 8. Exterior Lighting <ul><li>Headlight Switch Control </li></ul><ul><ul><li>Headlight switch controls the following lights: </li></ul></ul><ul><ul><ul><li>Side-marker lights </li></ul></ul></ul><ul><ul><ul><li>Front parking lights </li></ul></ul></ul>
    • 9. Exterior Lighting <ul><li>Headlight Switch Control </li></ul><ul><ul><li>Headlight switch controls the following lights: </li></ul></ul><ul><ul><ul><li>Dash lights </li></ul></ul></ul><ul><ul><ul><li>Interior (dome) light(s) </li></ul></ul></ul>
    • 10. Exterior Lighting <ul><li>Computer Controlled Lights </li></ul><ul><ul><li>A typical computer-controlled lighting system usually includes following steps: </li></ul></ul><ul><ul><ul><li>STEP 1: The driver depresses or rotates the headlight switch. </li></ul></ul></ul>
    • 11. Exterior Lighting <ul><li>Computer Controlled Lights </li></ul><ul><ul><li>A typical computer-controlled lighting system usually includes following steps: </li></ul></ul><ul><ul><ul><li>STEP 2: The signal from the headlight switch is sent to the nearest control module. </li></ul></ul></ul>
    • 12. Exterior Lighting <ul><li>Computer Controlled Lights </li></ul><ul><ul><li>A typical computer-controlled lighting system usually includes following steps: </li></ul></ul><ul><ul><ul><li>STEP 3: The control module then sends a request to the headlight control module. </li></ul></ul></ul>
    • 13. Exterior Lighting <ul><li>Computer Controlled Lights </li></ul><ul><ul><li>A typical computer-controlled lighting system usually includes following steps: </li></ul></ul><ul><ul><ul><li>STEP 4: All modules monitor current flow through the circuit. </li></ul></ul></ul>
    • 14. Exterior Lighting <ul><li>Computer Controlled Lights </li></ul><ul><ul><li>A typical computer-controlled lighting system usually includes following steps: </li></ul></ul><ul><ul><ul><li>STEP 5: After the ignition has been turned off, the modules will turn off the lights. </li></ul></ul></ul>
    • 15. Exterior Lighting <ul><li>Trade Number </li></ul><ul><ul><li>The number used on automotive bulbs is called the bulb trade number, as recorded with the American National Standards Institute (ANSI). </li></ul></ul>
    • 16. Figure 56-1 Dual-filament (double-contact) bulbs contain both a low-intensity filament for taillights or parking lights and a high-intensity filament for brake lights and turn signals. Bulbs come in a variety of shapes and sizes. The numbers shown are the trade numbers.
    • 17. BULB NUMBERS
    • 18. Bulb Numbers <ul><li>Candlepower </li></ul><ul><ul><li>The trade number also identifies the size, shape, number of filaments, and amount of light produced, measured in candlepower. </li></ul></ul>
    • 19. Chart 56-1 Bulbs that have the same trade number have the same operating voltage and wattage. The NA means that the bulb uses a natural amber glass ampoule with clear turn signal lenses.
    • 20. Chart 56-1 (continued) Bulbs that have the same trade number have the same operating voltage and wattage. The NA means that the bulb uses a natural amber glass ampoule with clear turn signal lenses.
    • 21. Bulb Numbers <ul><li>Bulb Number Suffixes </li></ul><ul><ul><li>Typical bulb suffixes include: </li></ul></ul><ul><ul><ul><li>NA: natural amber (amber glass) </li></ul></ul></ul><ul><ul><ul><li>A: amber (painted glass) </li></ul></ul></ul>
    • 22. Bulb Numbers <ul><li>Bulb Number Suffixes </li></ul><ul><ul><li>Typical bulb suffixes include: </li></ul></ul><ul><ul><ul><li>HD: heavy duty </li></ul></ul></ul><ul><ul><ul><li>LL: long life </li></ul></ul></ul>
    • 23. Bulb Numbers <ul><li>Bulb Number Suffixes </li></ul><ul><ul><li>Typical bulb suffixes include: </li></ul></ul><ul><ul><ul><li>IF: inside frosted </li></ul></ul></ul><ul><ul><ul><li>R: red </li></ul></ul></ul>
    • 24. Bulb Numbers <ul><li>Bulb Number Suffixes </li></ul><ul><ul><li>Typical bulb suffixes include: </li></ul></ul><ul><ul><ul><li>B: blue </li></ul></ul></ul><ul><ul><ul><li>G: green </li></ul></ul></ul>
    • 25. Figure 56-2 Bulbs that have the same trade number have the same operating voltage and wattage. The NA means that the bulb uses a natural amber glass ampoule with clear turn signal lenses.
    • 26. Bulb Numbers <ul><li>Testing Bulbs </li></ul><ul><ul><li>Bulbs can be tested using two basic tests: </li></ul></ul><ul><ul><ul><li>Perform a visual inspection of any bulb. </li></ul></ul></ul>
    • 27. Bulb Numbers <ul><li>Testing Bulbs </li></ul><ul><ul><li>Bulbs can be tested using two basic tests: </li></ul></ul><ul><ul><ul><li>Bulbs can be tested using an ohmmeter. </li></ul></ul></ul>
    • 28. Figure 56-3 Close-up a 2057 dual-filament (double-contact) bulb that failed. Notice that the top filament broke from its mounting and melted onto the lower filament. This bulb caused the dash lights to come on whenever the brakes were applied.
    • 29. Figure 56-4 Corrosion caused the two terminals of this dual-filament bulb to be electrically connected.
    • 30. Figure 56-5 Often the best diagnosis is a thorough visual inspection. This bulb was found to be filled with water, which caused weird problems.
    • 31. Figure 56-6 This single-filament bulb is being tested with a digital multimeter set to read resistance in ohms. The reading of 1.1 ohms is the resistance of the bulb when cold. As soon as current flows through the filament, the resistance increases about 10 times. It is the initial surge of current flowing through the filament when the bulb is cool that causes many bulbs to fail in cold weather as a result of the reduced resistance. As the temperature increases, the resistance increases.
    • 32. BRAKE LIGHTS
    • 33. Brake Lights <ul><li>Operation </li></ul><ul><ul><li>Brake lights (stop lights) use the high-intensity filament of a double-filament bulb. </li></ul></ul>
    • 34. Brake Lights <ul><li>Operation </li></ul><ul><ul><li>When the brakes are applied, the brake switch is closed and the brake lamps light. </li></ul></ul>
    • 35. Brake Lights <ul><li>Operation </li></ul><ul><ul><li>The brake switch receives current from a fuse that is hot all the time. </li></ul></ul><ul><ul><li>The brake light switch is a normally open (N.O.) switch, but is closed when the driver depresses the brake pedal. </li></ul></ul>
    • 36. Brake Lights <ul><li>Operation </li></ul><ul><ul><li>Since 1986, all vehicles sold in the United States have a third brake light commonly referred to as the center high-mounted stop light (CHMSL). </li></ul></ul>
    • 37. Brake Lights <ul><li>Operation </li></ul><ul><ul><li>The brake switch is also used as an input switch (signal) for the following: </li></ul></ul><ul><ul><ul><li>Cruise control (deactivates when the brake pedal is depressed) </li></ul></ul></ul>
    • 38. Brake Lights <ul><li>Operation </li></ul><ul><ul><li>The brake switch is also used as an input switch (signal) for the following: </li></ul></ul><ul><ul><ul><li>Antilock brakes (ABS) </li></ul></ul></ul>
    • 39. Brake Lights <ul><li>Operation </li></ul><ul><ul><li>The brake switch is also used as an input switch (signal) for the following: </li></ul></ul><ul><ul><ul><li>Brake shift interlock (prevents shifting from park position unless the brake pedal is depressed). </li></ul></ul></ul>?
    • 40. Figure 56-7 Typical brake light and taillight circuit showing the brake switch and all of the related circuit components.
    • 41. TURN SIGNALS
    • 42. Turn Signals <ul><li>Operation </li></ul><ul><ul><li>The turn signal circuit is powered by the ignition switch and operated by a lever and switch. </li></ul></ul>
    • 43. Turn Signals <ul><li>Operation </li></ul><ul><ul><li>When the turn signal switch is moved, the corresponding turn signal lamps receive current through the flasher unit. </li></ul></ul>
    • 44. Turn Signals <ul><li>Operation </li></ul><ul><ul><li>The flasher unit causes the current to start and stop as the turn signal lamp flashes on and off. </li></ul></ul>
    • 45. Figure 56-9 The typical turn signal switch includes various springs and cams to control the switch and to cause the switch to cancel after a turn has been completed.
    • 46. Turn Signals <ul><li>One-Filament Stop Turn Bulbs </li></ul><ul><ul><li>In many vehicles, the stop and turn signals are both provided by one filament. </li></ul></ul>
    • 47. Turn Signals <ul><li>One-Filament Stop Turn Bulbs </li></ul><ul><ul><li>When the stop lamps and turn signals share a common bulb filament, stop light current flows through the turn signal switch. </li></ul></ul>
    • 48. Figure 56-10 When the stop lamps and turn signals share a common bulb filament, stop light current flows through the turn signal switch.
    • 49. Turn Signals <ul><li>Two-Filament Stop Turn Bulbs </li></ul><ul><ul><li>Brake and turn signal switches are not connected. </li></ul></ul>
    • 50. Turn Signals <ul><li>Two-Filament Stop Turn Bulbs </li></ul><ul><ul><li>For example, when a right turn is signaled, the turn signal switch contacts send flasher current to the right-hand filament and brake switch current to the left-hand filament. </li></ul></ul>
    • 51. Figure 56-11 When a right turn in signaled, the turn signal switch contacts send flasher current to the right-hand filament and brake switch current to the left-hand filament.
    • 52. Turn Signals <ul><li>Flasher Units </li></ul><ul><ul><li>A turn signal flasher unit is a metal or plastic can containing a switch that opens and closes the turn signal circuit. </li></ul></ul>
    • 53. Turn Signals <ul><li>Flasher Units </li></ul><ul><ul><li>There are many different types of flasher units: </li></ul></ul><ul><ul><ul><li>DOT flashers </li></ul></ul></ul><ul><ul><ul><li>Bimetal flashers </li></ul></ul></ul>
    • 54. Turn Signals <ul><li>Flasher Units </li></ul><ul><ul><li>There are many different types of flasher units: </li></ul></ul><ul><ul><ul><li>Hybrid flashers </li></ul></ul></ul><ul><ul><ul><li>Solid-state flashers </li></ul></ul></ul>
    • 55. Figure 56-12 Two styles of two-prong flasher units.
    • 56. Turn Signals <ul><li>Electronic Flasher Replacement Units </li></ul><ul><ul><li>Most turn signal flasher units are mounted in a metal clip attached to the dash. </li></ul></ul>
    • 57. Turn Signals <ul><li>Electronic Flasher Replacement Units </li></ul><ul><ul><li>Most four-way hazard flasher units and some turn signal flasher units are plugged into the fuse panel. </li></ul></ul>
    • 58. Turn Signals <ul><li>Electronic Flasher Replacement Units </li></ul><ul><ul><li>With both the turn signal and the ignition on, listen and/or feel for the clicking of the flasher unit to find the location of the flasher unit. </li></ul></ul>
    • 59. Turn Signals <ul><li>Electronic Flasher Replacement Units </li></ul><ul><ul><li>Newer vehicles have electronic flashers that use microchips to control the on/off function. </li></ul></ul>
    • 60. Turn Signals <ul><li>Electronic Flasher Replacement Units </li></ul><ul><ul><li>Electronic flashers are compatible with older systems: </li></ul></ul><ul><ul><ul><li>Electronic flashers do not burn out. </li></ul></ul></ul>
    • 61. Turn Signals <ul><li>Electronic Flasher Replacement Units </li></ul><ul><ul><li>Electronic flashers are compatible with older systems: </li></ul></ul><ul><ul><ul><li>If upgrading to LED tail lamps, or lights, the LED bulbs only work with electronic. </li></ul></ul></ul>
    • 62. Turn Signals <ul><li>Hazard Warning Flasher </li></ul><ul><ul><li>The hazard warning flasher (also called a parallel or variable-load flasher) is a device installed in a vehicle lighting system with the primary function of causing both the left and right turn signal lamps to flash when the hazard warning switch is activated. </li></ul></ul>
    • 63. Turn Signals <ul><li>Hazard Warning Flasher </li></ul><ul><ul><li>Secondary functions may include visible dash indicators for the hazard system and an audible signal to indicate when the flasher is operating. </li></ul></ul>
    • 64. Figure 56-13 A hazard warning flasher uses a parallel resistor across the contacts to provide a constant flashing rate regardless of the number of bulbs used in the circuit.
    • 65. Turn Signals <ul><li>Combination Turn Signal and Hazard Warning Flasher </li></ul><ul><ul><li>The combination flasher is a device that combines the functions of a turn signal flasher and a hazard warning flasher into one package, which often uses three electrical terminals. </li></ul></ul>? ?
    • 66. Figure 56-14 The side-marker light goes out whenever there is voltage at both points X and Y. These opposing voltages stop current flow through the side-marker light. The left turn light and left park light are actually the same bulb (usually 2057) and are shown separately to help explain how the side-marker light works on many vehicles.
    • 67. HEADLIGHTS
    • 68. Headlights <ul><li>Headlight Switches </li></ul><ul><ul><li>The headlight switch operates the exterior and interior lights of most vehicles. </li></ul></ul>
    • 69. Headlights <ul><li>Headlight Switches </li></ul><ul><ul><li>On noncomputer-controlled lighting systems, the headlight switch is connected directly to the battery through a fusible link, and has continuous power or is “hot” all the time. </li></ul></ul>
    • 70. Headlights <ul><li>Headlight Switches </li></ul><ul><ul><li>A circuit breaker is built into older model headlight switches to protect the headlight circuit. </li></ul></ul>
    • 71. Headlights <ul><li>Headlight Switches </li></ul><ul><ul><li>The headlight switch may include the following: </li></ul></ul><ul><ul><ul><li>The interior dash lights can often be dimmed manually by rotating the headlight switch knob or by a variable resistor (called a rheostat). </li></ul></ul></ul>
    • 72. Headlights <ul><li>Headlight Switches </li></ul><ul><ul><li>The headlight switch may include the following: </li></ul></ul><ul><ul><ul><li>A built-in circuit breaker that will rapidly turn the headlights on and off in the event of a short circuit. </li></ul></ul></ul>
    • 73. Figure 56-15 Typical headlight circuit diagram. Note that the headlight switch is represented by a dotted outline indicating that other circuits (such as dash lights) also operate from the switch.
    • 74. Headlights <ul><li>Automatic Headlights </li></ul><ul><ul><li>Computer-controlled lights use a light sensor. </li></ul></ul><ul><ul><li>The sensor is mounted on the dashboard or mirror. </li></ul></ul>
    • 75. Headlights <ul><li>Sealed Beam Headlights </li></ul><ul><ul><li>A sealed glass or plastic assembly contains the bulb, reflective surface, and prism lenses to properly focus the light beam. </li></ul></ul>
    • 76. Headlights <ul><li>Sealed Beam Headlights </li></ul><ul><ul><li>Low-beam headlights contain two filaments </li></ul></ul><ul><ul><ul><li>One for low beam </li></ul></ul></ul><ul><ul><ul><li>One for high beam </li></ul></ul></ul>
    • 77. Headlights <ul><li>Sealed Beam Headlights </li></ul><ul><ul><li>Low-beam headlights contain two filaments </li></ul></ul><ul><ul><ul><li>Common ground </li></ul></ul></ul>
    • 78. Headlights <ul><li>Sealed Beam Headlights </li></ul><ul><ul><li>High-beam headlights contain only one filament and two terminals. </li></ul></ul><ul><ul><li>Entire headlight assembly must be replaced if either filament is defective. </li></ul></ul>
    • 79. Headlights <ul><li>Sealed Beam Headlights </li></ul><ul><ul><li>A sealed beam headlight can be tested with an ohmmeter. </li></ul></ul>
    • 80. Figure 56-16 A typical four-headlight system using sealed beam headlights.
    • 81. Headlights <ul><li>Halogen Sealed Beam Headlights </li></ul><ul><ul><li>Halogen sealed beam headlights are brighter and more expensive than normal headlights. </li></ul></ul>
    • 82. Headlights <ul><li>Halogen Sealed Beam Headlights </li></ul><ul><ul><li>The candlepower output would exceed the maximum U.S. federal standards if all four halogen headlights were on. </li></ul></ul>
    • 83. Headlights <ul><li>Halogen Sealed Beam Headlights </li></ul><ul><ul><li>Before trying to repair the problem that only two of the four lamps are on, check the owner or shop manual for proper operation. </li></ul></ul>
    • 84. Headlights <ul><li>Halogen Sealed Beam Headlights </li></ul><ul><ul><li>CAUTION: Do not attempt to wire all headlights together. The extra current flow could overheat the wiring from the headlight switch through the dimmer switch and to the headlights. The overloaded circuit could cause a fire. </li></ul></ul>
    • 85. Headlights <ul><li>Composite Headlights </li></ul><ul><ul><li>Composite headlights are constructed using a replaceable bulb and a fixed lens cover that is part of the vehicle. </li></ul></ul>
    • 86. Headlights <ul><li>Composite Headlights </li></ul><ul><ul><li>The replaceable bulbs are usually bright halogen bulbs. </li></ul></ul>?
    • 87. Figure 56-17 A typical composite headlamp assembly. The lens, housing, and bulb sockets are usually included as a complete assembly.
    • 88. HIGH-INTENSITY DISCHARGE HEADLIGHTS
    • 89. High-Intensity Discharge Headlights <ul><li>Parts and Operation </li></ul><ul><ul><li>High-intensity discharge (HID) headlights produce a distinctive blue-white light that is crisper, clearer, and brighter than a halogen headlight. </li></ul></ul>
    • 90. High-Intensity Discharge Headlights <ul><li>Parts and Operation </li></ul><ul><ul><li>These headlights do not use a filament. </li></ul></ul>
    • 91. High-Intensity Discharge Headlights <ul><li>Parts and Operation </li></ul><ul><ul><li>A high-voltage pulse is sent to the bulb, which arcs across the tips of electrodes producing light. </li></ul></ul>
    • 92. High-Intensity Discharge Headlights <ul><li>Parts and Operation </li></ul><ul><ul><li>It produces twice the light with less electrical input. </li></ul></ul><ul><ul><li>The HID lighting system consists of the discharge arc source, igniter, ballast, and headlight assembly. </li></ul></ul>
    • 93. High-Intensity Discharge Headlights <ul><li>Parts and Operation </li></ul><ul><ul><li>HID headlights are also called xenon headlights. </li></ul></ul><ul><ul><li>The color of light is expressed in temperature using the Kelvin scale. </li></ul></ul>
    • 94. High-Intensity Discharge Headlights <ul><li>Parts and Operation </li></ul><ul><ul><li>Typical color temperatures include: </li></ul></ul><ul><ul><ul><li>Daylight: 5,400°K </li></ul></ul></ul><ul><ul><ul><li>HID: 4,100°K </li></ul></ul></ul><ul><ul><ul><li>Halogen: 3,200°K </li></ul></ul></ul>
    • 95. High-Intensity Discharge Headlights <ul><li>Parts and Operation </li></ul><ul><ul><li>Typical color temperatures include: </li></ul></ul><ul><ul><ul><li>Incandescent (tungsten): 2,800°K </li></ul></ul></ul><ul><ul><li>The HID ballast is powered by 12 volts from the headlight switch. </li></ul></ul>
    • 96. High-Intensity Discharge Headlights <ul><li>Parts and Operation </li></ul><ul><ul><li>The HID headlights operate in three stages or states: </li></ul></ul><ul><ul><ul><li>Start-up or stroke state </li></ul></ul></ul><ul><ul><ul><li>Run-up state </li></ul></ul></ul><ul><ul><ul><li>Steady state </li></ul></ul></ul>
    • 97. Figure 56-19 The igniter contains the ballast and transformer needed to provide high-voltage pulses to the arc tube bulb.
    • 98. Figure 56-20 HID (xenon) headlights emit a whiter light than halogen headlights and usually look blue compared to halogen bulbs.
    • 99. High-Intensity Discharge Headlights <ul><li>Start-Up or Stroke State </li></ul><ul><ul><li>The ballast may draw up to 20 amperes at 12 volts. </li></ul></ul><ul><ul><li>The ballast sends multiple high-voltage pulses to the arc tube. </li></ul></ul>
    • 100. High-Intensity Discharge Headlights <ul><li>Start-Up or Stroke State </li></ul><ul><ul><li>The voltage provided by the ballast during the start-up state ranges from −600 volts to +600 volts, which is increased by a transformer to about 25,000 volts. </li></ul></ul>
    • 101. High-Intensity Discharge Headlights <ul><li>Run-Up State </li></ul><ul><ul><li>The ballast provides a higher than steady state voltage to the arc tube to keep the bulb illuminated. </li></ul></ul><ul><ul><li>On a cold bulb, this state could last as long as 40 seconds. </li></ul></ul>
    • 102. High-Intensity Discharge Headlights <ul><li>Run-Up State </li></ul><ul><ul><li>On a hot bulb, the run-up state may last only 15 seconds. </li></ul></ul><ul><ul><li>The current requirements during this state are about 360 volts from the ballast and a power level of about 75 watts. </li></ul></ul>
    • 103. High-Intensity Discharge Headlights <ul><li>Steady State </li></ul><ul><ul><li>This phase begins when the power requirement of the bulb drops to 35 watts. </li></ul></ul>
    • 104. High-Intensity Discharge Headlights <ul><li>Steady State </li></ul><ul><ul><li>The ballast provides a minimum of 55 volts to the bulb during operation in this state. </li></ul></ul>
    • 105. High-Intensity Discharge Headlights <ul><li>Bi-Xenon Headlights </li></ul><ul><ul><li>These lights use a shutter to block some light during low-beam operation and then mechanically move to expose more of the light from the bulb for high-beam operation. </li></ul></ul>
    • 106. High-Intensity Discharge Headlights <ul><li>Bi-Xenon Headlights </li></ul><ul><ul><li>Vehicles equipped with bi-xenon headlights use two halogen lights for the “flash-to-pass” feature. </li></ul></ul>
    • 107. High-Intensity Discharge Headlights <ul><li>Failure Symptoms </li></ul><ul><ul><li>Following symptoms indicate bulb failure: </li></ul></ul><ul><ul><ul><li>A light flickers. </li></ul></ul></ul><ul><ul><ul><li>Lights go out. </li></ul></ul></ul><ul><ul><ul><li>Color changes to a dim pink glow. </li></ul></ul></ul>
    • 108. High-Intensity Discharge Headlights <ul><li>Diagnosis and Service </li></ul><ul><ul><li>High-intensity discharge headlights will change slightly in color with age. </li></ul></ul><ul><ul><li>This color shift is usually not noticeable unless one headlight arc tube assembly has been replaced. </li></ul></ul>
    • 109. High-Intensity Discharge Headlights <ul><li>Diagnosis and Service </li></ul><ul><ul><li>An old arc tube assembly may not light immediately if it is turned off and then back on immediately ( “hot restrike”) and a replacement may be needed. </li></ul></ul>
    • 110. LED HEADLIGHTS
    • 111. LED Headlights <ul><li>Some vehicles use LED headlights </li></ul><ul><ul><li>Advantages include: </li></ul></ul><ul><ul><ul><li>Long service life. </li></ul></ul></ul><ul><ul><ul><li>Reduced electrical power required. </li></ul></ul></ul>
    • 112. LED Headlights <ul><li>Some vehicles use LED headlights </li></ul><ul><ul><li>Disadvantages include: </li></ul></ul><ul><ul><ul><li>High cost. </li></ul></ul></ul><ul><ul><ul><li>Many small LEDs required to create the necessary light output. </li></ul></ul></ul>
    • 113. Figure 56-21 LED headlights usually require multiple units to provide the needed light as seen on this Lexus LS600h.
    • 114. HEADLIGHT AIMING
    • 115. Headlight Aiming <ul><li>By law, all headlights must be able to be aimed using headlight aiming equipment. </li></ul><ul><li>Older vehicles equipped with sealed beam headlights used a headlight aiming system that attached to the headlight itself. </li></ul>
    • 116. Figure 56-22 Typical headlight aiming diagram as found in service information.
    • 117. Figure 56-23 Many composite headlights have a built-in bubble level to make aiming easy and accurate.
    • 118. ADAPTIVE FRONT LIGHTING SYSTEM
    • 119. Adaptive Front Lighting System <ul><li>Parts and Operation </li></ul><ul><ul><li>Adaptive (or advanced) front light system, or AFS mechanically moves the headlights to follow the direction of the front wheels. </li></ul></ul>
    • 120. Adaptive Front Lighting System <ul><li>Parts and Operation </li></ul><ul><ul><li>The headlights are usually capable of rotating 15 degrees to the left and 5 degrees to the right. </li></ul></ul>
    • 121. Adaptive Front Lighting System <ul><li>Parts and Operation </li></ul><ul><ul><li>AFS is often used in addition to self-leveling motors so that the headlights remain properly aimed. </li></ul></ul>
    • 122. Adaptive Front Lighting System <ul><li>Parts and Operation </li></ul><ul><ul><li>NOTE: These angles are reversed on vehicles sold in countries that drive on the left side of the road, such as Great Britain, Japan, Australia, and New Zealand. </li></ul></ul>
    • 123. Figure 56-24 Adaptive front lighting systems rotate the low-beam headlight in the direction of travel.
    • 124. Figure 56-25 A typical adaptive front lighting system uses two motors: one for the up and down movement and the other for rotating the low-beam headlight to the left and right.
    • 125. Adaptive Front Lighting System <ul><li>Diagnosis and Service </li></ul><ul><ul><li>Steps when diagnosing AFS fault: </li></ul></ul><ul><ul><ul><li>Start by checking that the AFS is switched on. Most AFS headlights are equipped with a switch that allows the driver to turn the system on and off. </li></ul></ul></ul>
    • 126. Adaptive Front Lighting System <ul><li>Diagnosis and Service </li></ul><ul><ul><li>Steps when diagnosing AFS fault: </li></ul></ul><ul><ul><ul><li>Check that the system performs a self-test during start-up. </li></ul></ul></ul>
    • 127. Adaptive Front Lighting System <ul><li>Diagnosis and Service </li></ul><ul><ul><li>Steps when diagnosing AFS fault: </li></ul></ul><ul><ul><ul><li>Verify that both low-beam and high-beam lights function correctly. The system may be disabled if a fault with one of the headlights is detected. </li></ul></ul></ul>
    • 128. Adaptive Front Lighting System <ul><li>Diagnosis and Service </li></ul><ul><ul><li>First step when diagnosing AFS fault is to: </li></ul></ul><ul><ul><ul><li>Use a scan tool to test for any AFS-related diagnostic trouble codes. Some systems allow the AFS to be checked and operated using a scan tool. </li></ul></ul></ul>
    • 129. Figure 56-26 Typical dash-mounted switch that allows the driver to disable the front lighting system.
    • 130. DAYTIME RUNNING LIGHTS
    • 131. Daytime Running Lights <ul><li>Purpose and Function </li></ul><ul><ul><li>Daytime running lights (DRLs): </li></ul></ul><ul><ul><ul><li>Front parking lights. </li></ul></ul></ul><ul><ul><ul><li>Separate DRL lamps. </li></ul></ul></ul>
    • 132. Daytime Running Lights <ul><li>Purpose and Function </li></ul><ul><ul><li>Daytime running lights (DRLs): </li></ul></ul><ul><ul><ul><li>Headlights (usually at reduced current and voltage) when the vehicle is running. </li></ul></ul></ul>
    • 133. Daytime Running Lights <ul><li>Purpose and Function </li></ul><ul><ul><li>Daytime running lights (DRLs): </li></ul></ul><ul><ul><ul><li>Daytime running lights primarily use a control module that turns on either the low or high-beam headlights or separate daytime running lights. </li></ul></ul></ul>
    • 134. Daytime Running Lights <ul><li>Purpose and Function </li></ul><ul><ul><li>CAUTION: Most factory daytime running lights operate the headlights at reduced intensity. These are not designed to be used at night. Normal intensity of the headlights (and operation of the other external lamps) is actuated by turning on the headlights as usual. </li></ul></ul>
    • 135. Figure 56-27 Typical daytime running light (DRL) circuit. Follow the arrows from the DRL module through both headlights. Notice that the left and right headlights are connected in series, resulting in increased resistance, less current flow, and dimmer than normal lighting. When the normal headlights are turned on, both headlights receive full battery voltage, with the left headlight grounding through the DRL module.
    • 136. DIMMER SWITCHES
    • 137. Dimmer Switches <ul><li>A current is sent to the dimmer switch, which allows the current to flow to either the high-beam or the low-beam filament of the headlight bulb. </li></ul>
    • 138. Dimmer Switches <ul><li>The dimmer switch is usually hand operated by a lever on the steering column. </li></ul>
    • 139. Figure 56-28 Most vehicles use positive switching of the high- and low-beam headlights. Notice that both filaments share the same ground connection. Some vehicles use negative switching and place the dimmer switch between the filaments and the ground.
    • 140. COURTESY LIGHTS
    • 141. Courtesy Lights <ul><li>Courtesy light is a generic term primarily used for interior lights, including overhead (dome) and under-the-dash (courtesy) lights. </li></ul>
    • 142. Courtesy Lights <ul><li>These lights are controlled by switches located in the doorjambs of the vehicle or by a switch on the dash. </li></ul>
    • 143. Figure 56-29 A typical courtesy light doorjamb switch. Newer vehicles use the door switch as an input to the vehicle computer and the computer turns the interior lights on or off. By placing the lights under the control of the computer, the vehicle engineers have the opportunity to delay the lights after the door is closed and to shut them off after a period of time to avoid draining the battery.
    • 144. ILLUMINATED ENTRY
    • 145. Illuminated Entry <ul><li>The interior lights are turned on for a given amount of time when the outside door handle is operated while the doors are locked. </li></ul><ul><li>Most vehicles also light the exterior door keyhole. </li></ul>
    • 146. FIBER OPTICS
    • 147. Fiber Optics <ul><li>Fiber optics is the transmission of light through special plastic (polymethyl methacrylate) that keeps the light rays parallel. </li></ul>
    • 148. Fiber Optics <ul><li>Some vehicles are equipped with fender-mounted units that light when the lights or turn signals are operating. </li></ul>
    • 149. Fiber Optics <ul><li>Plastic fiber-optic strands often transmit the light at the bulb to the indicator on top of the fender so that the driver can determine if a certain light is operating. </li></ul>
    • 150. Fiber Optics <ul><li>Fiber-optics are also commonly used to light ashtrays, outside door locks, and other areas where a small amount of light is required. </li></ul>
    • 151. AUTOMATIC DIMMING MIRRORS
    • 152. Automatic Dimming Mirrors <ul><li>Parts and Operation </li></ul><ul><ul><li>Automatic dimming mirrors use electrochromic technology to dim the mirror in proportion to the amount of headlight glare from other vehicles at the rear. </li></ul></ul>
    • 153. Automatic Dimming Mirrors <ul><li>Parts and Operation </li></ul><ul><ul><li>This technology uses a gel that changes with light between two pieces of glass. </li></ul></ul>
    • 154. Automatic Dimming Mirrors <ul><li>Parts and Operation </li></ul><ul><ul><li>One piece of glass acts as a reflector and the other has a transparent (clear) electrically conductive coating. </li></ul></ul>
    • 155. Automatic Dimming Mirrors <ul><li>Parts and Operation </li></ul><ul><ul><li>The inside rearview mirror also has a forward-facing light sensor. </li></ul></ul>
    • 156. Automatic Dimming Mirrors <ul><li>Parts and Operation </li></ul><ul><ul><li>The rearward-facing sensor sends a voltage to the electrochromic gel in the mirror that is in proportion to the amount of glare detected. </li></ul></ul>
    • 157. Automatic Dimming Mirrors <ul><li>Parts and Operation </li></ul><ul><ul><li>The mirror dims then becomes like a standard rearview mirror when the glare is no longer detected. </li></ul></ul>
    • 158. Automatic Dimming Mirrors <ul><li>Parts and Operation </li></ul><ul><ul><li>If automatic dimming mirrors are used on the exterior, the sensors in the interior mirror and electronics are used to control both the interior and exterior mirrors. </li></ul></ul>
    • 159. Figure 56-30 An automatic dimming mirror compares the amount of light toward the front of the vehicle to the rear of the vehicle and allies a voltage to cause the gel to darken the mirror.
    • 160. Automatic Dimming Mirrors <ul><li>Diagnosis and Service </li></ul><ul><ul><li>Most dimming mirrors have a green light to indicate the presence of electrical power. </li></ul></ul>
    • 161. Automatic Dimming Mirrors <ul><li>Diagnosis and Service </li></ul><ul><ul><li>If no voltage is found, follow standard troubleshooting procedures to find the cause. </li></ul></ul>
    • 162. Automatic Dimming Mirrors <ul><li>Diagnosis and Service </li></ul><ul><ul><li>If the mirror is getting voltage, start the diagnosis by placing a strip of tape over the forward-facing light sensor. </li></ul></ul>
    • 163. Automatic Dimming Mirrors <ul><li>Diagnosis and Service </li></ul><ul><ul><li>Turn the ignition key on, engine off (KOEO), and observe the operation of the mirror when a flashlight or trouble light is directed onto it. </li></ul></ul>
    • 164. Automatic Dimming Mirrors <ul><li>Diagnosis and Service </li></ul><ul><ul><li>If the mirror reacts and dims, the forward-facing sensor is defective. </li></ul></ul><ul><ul><li>Most often, the entire mirror assembly has to be replaced if any sensor or mirror faults are found. </li></ul></ul>
    • 165. Automatic Dimming Mirrors <ul><li>Diagnosis and Service </li></ul><ul><ul><li>One typical fault with automatic dimming mirrors is a crack can occur in the mirror assembly, allowing the gel to escape from between the two layers of glass. </li></ul></ul>
    • 166. Automatic Dimming Mirrors <ul><li>Diagnosis and Service </li></ul><ul><ul><li>The mirror should be replaced at the first sign of any gel leakage. </li></ul></ul>?
    • 167. FEEDBACK
    • 168. Feedback <ul><li>Definition </li></ul><ul><ul><li>When current that lacks a good ground goes backward along the power side of the circuit in search of a return path (ground) to the battery, this reverse flow is called feedback. </li></ul></ul>
    • 169. Feedback <ul><li>Feedback Example </li></ul><ul><ul><li>A customer complained that when the headlights were on, the left turn signal indicator light on the dash remained on. The cause was found to be a poor ground connection for the left front parking light socket. </li></ul></ul>
    • 170. Feedback <ul><li>Feedback Example </li></ul><ul><ul><li>A corroded socket did not provide a good enough ground to conduct all current required to light the dim filament of the bulb. </li></ul></ul>
    • 171. Feedback <ul><li>Feedback Example </li></ul><ul><ul><li>The two filaments of the bulb share the same ground connection and are electrically connected. </li></ul></ul>
    • 172. Feedback <ul><li>Feedback Example </li></ul><ul><ul><li>When all the current could not flow through the bulb ’s ground in the socket, it caused a feedback or reversed its flow through the other filament, looking for ground. </li></ul></ul>
    • 173. LIGHTING SYSTEM DIAGNOSIS
    • 174. Lighting System Diagnosis <ul><li>Diagnosing any faults in the lighting and signaling systems usually includes the following steps: </li></ul><ul><ul><li>STEP 1: Verify the customer concern. </li></ul></ul>
    • 175. Lighting System Diagnosis <ul><li>Diagnosing any faults in the lighting and signaling systems usually includes the following steps: </li></ul><ul><ul><li>STEP 2: Perform a visual inspection, checking for collision damage or other possible causes that would affect the operation of the lighting circuit. </li></ul></ul>
    • 176. Lighting System Diagnosis <ul><li>Diagnosing any faults in the lighting and signaling systems usually includes the following steps: </li></ul><ul><ul><li>STEP 3: Connect a factory or enhanced scan tool with bidirectional control of the computer modules to check for proper operation of the affected lighting circuit. </li></ul></ul>
    • 177. Lighting System Diagnosis <ul><li>Diagnosing any faults in the lighting and signaling systems usually includes the following steps: </li></ul><ul><ul><li>STEP 4: Follow the diagnostic procedure as found in service information to determine the root cause of the problem. </li></ul></ul>
    • 178. LIGHTING SYSTEM SYMPTOM GUIDE
    • 179. The following list will assist technicians in troubleshooting lighting systems.
    • 180. The following list will assist technicians in troubleshooting lighting systems.
    • 181. The following list will assist technicians in troubleshooting lighting systems.
    • 182. TAILLIGHT BULB REPLACEMENT 1 The driver noticed that the taillight fault indicator (icon) on the dash was on any time the lights were on.
    • 183. TAILLIGHT BULB REPLACEMENT 2 A visual inspection at the rear of the vehicle indicated that the right rear taillight bulb did not light. Removing a few screws from the plastic cover revealed the taillight assembly.
    • 184. TAILLIGHT BULB REPLACEMENT 3 The bulb socket is removed from the taillight assembly by gently twisting the base of the bulb counterclockwise.
    • 185. TAILLIGHT BULB REPLACEMENT 4 The bulb is removed from the socket by gently grasping the bulb and pulling the bulb straight out of the socket. Many bulbs required that you rotate the bulb 90° (1/4 turn) to release the retaining bulbs.
    • 186. TAILLIGHT BULB REPLACEMENT 5 The new 7443 replacement bulb is being checked with an ohmmeter to be sure that it is okay before it is installed in the vehicle.
    • 187. TAILLIGHT BULB REPLACEMENT 6 The replacement bulb in inserted into the taillight socket and the lights are turned on to verify proper operation before putting the components back together.
    • 188. OPTICAL HEADLIGHT AIMING 1 Before checking the vehicle for headlight aim, be sure that all the tires are at the correct inflation pressure, and that the suspension is in good working condition.
    • 189. OPTICAL HEADLIGHT AIMING 2 The headlight aim equipment will have to be adjusted for the slope of the floor in the service bay. Start the process by turning on the laser light generator on the side of the aimer body.
    • 190. OPTICAL HEADLIGHT AIMING 3 Place a yardstick or measuring tape vertically in front of the center of the front wheel, noting the height of the laser beam.
    • 191. OPTICAL HEADLIGHT AIMING 4 Move the yardstick to the center of the rear wheel and measure the height of the laser beam at this point. The height at the front and rear wheels should be the same.
    • 192. OPTICAL HEADLIGHT AIMING 5 If the laser beam height measurements are not the same, the floor slope of the aiming equipment must be adjusted. Turn the floor slope knob until the measurements are equal.
    • 193. OPTICAL HEADLIGHT AIMING 6 Place the aimer in front of the headlight to be checked, at a distance of 10 to 14 inches (25 to 35 cm). Use the aiming pointer to adjust the height of the aimer to the middle of the headlight.
    • 194. OPTICAL HEADLIGHT AIMING 7 Align the aimer horizontally, using the pointer to place the aimer at the center of the headlight.
    • 195. OPTICAL HEADLIGHT AIMING 8 Lateral alignment (aligning the body of the aimer with the body of the vehicle) is done by looking through the upper visor. The line in the upper visor is aligned with symmetrical points on the vehicle body.
    • 196. OPTICAL HEADLIGHT AIMING 9 Turn on the vehicle headlights, being sure to select the 9 correct beam position for the headlight to be aimed.
    • 197. OPTICAL HEADLIGHT AIMING 10 View the light beam through the aimer window. The position of the light pattern will be different for high and low beams.
    • 198. OPTICAL HEADLIGHT AIMING 11 If the first headlight is aimed adequately, move the aimer to the headlight on the opposite side of the vehicle. Follow the previous steps to position the aimer accurately.
    • 199. OPTICAL HEADLIGHT AIMING 12 If adjustment is required, move the headlight adjusting screws using a special tool or a 1/4-in. drive ratchet/socket combination. Watch the light beam through the aimer window to verify the adjustment.
    • 200. REAL WORLD FIX <ul><li>Weird Problem—Easy Solution </li></ul><ul><ul><li>A General Motors minivan had the following electrical problems. The turn signals flashed rapidly on the left side. With the ignition key off, the lights-on warning chime sounded if the brake pedal was depressed. When the brake pedal was depressed, the dome light came on. </li></ul></ul>BACK TO PRESENTATION <ul><li>All of these problems were caused by one defective 2057 dual-filament bulb, as shown in FIGURE 56–3. </li></ul><ul><li>Apparently, the two filaments were electrically connected when one filament broke and then welded to the other filament. This caused the electrical current to feed back from the brake light filament into the taillight circuit, causing all the problems. </li></ul><ul><ul><li>Figure 56-3 Close-up a 2057 dual-filament (double-contact) bulb that failed. Notice that the top filament broke from its mounting and melted onto the lower filament. This bulb caused the dash lights to come on whenever the brakes were applied. </li></ul></ul>
    • 201. FREQUENTLY ASKED QUESTION <ul><li>Why Are LEDs Used for Brake Lights? </li></ul><ul><ul><li>Light-emitting diode (LED) brake lights are frequently used for high-mounted stop lamps (CHMSLs) for the following reasons. </li></ul></ul>? BACK TO PRESENTATION <ul><ul><li>Faster illumination. An LED will light up to 200 milliseconds faster than an incandescent bulb, which requires some time to heat the filament before it is hot enough to create light. This faster illumination can mean the difference in stopping distances at 60 mph (100 km/h) by about 18 ft (6 m) due to the reduced reaction time for the driver of the vehicle behind. </li></ul></ul><ul><ul><li>Longer service life. LEDs are solid-state devices that do not use a filament to create light. As a result, they are less susceptible to vibration and will often last the life of the vehicle. </li></ul></ul><ul><li>NOTE: Aftermarket replacement LED bulbs that are used to replace conventional bulbs may require the use of a different type of flasher unit due to the reduced current draw of the LED bulbs </li></ul><ul><ul><li>Figure 56-8 A replacement LED taillight bulb is constructed of many small, individual light-emitting diodes. </li></ul></ul>
    • 202. FREQUENTLY ASKED QUESTION <ul><li>How Do You Tell What Type of Flasher Is Being Used? </li></ul><ul><ul><li>The easiest way to know which type of flasher can be used is to look at the type of bulb used in the tail lamps and turn signals. If it is a “wedge” style (plastic base, flat and rectangular), the vehicle has an electronic flasher. </li></ul></ul>? BACK TO PRESENTATION <ul><li>If it is a “twist and turn” bayonet-style (brass base) bulb, then either type of flasher can be used. </li></ul>
    • 203. FREQUENTLY ASKED QUESTION <ul><li>Why Does the Side-Marker Light Alternately Flash? </li></ul><ul><ul><li>A question that service technicians are asked frequently is why the side-marker light alternately goes out when the turn signal is on, and is on when the turn signal is off. Some vehicle owners think that there is a fault with the vehicle, but this is normal operation. </li></ul></ul>? <ul><li>The side-marker light goes out when the lights are on and the turn signal is flashing because there are 12 volts on both sides of the bulb (see points X and Y in FIGURE 56–14). </li></ul><ul><li>Normally, the side-marker light gets its ground through the turn signal bulb. </li></ul>BACK TO PRESENTATION <ul><ul><li>Figure 56-14 Always use meter leads that are CAT III rated on a meter that is also CAT III rated, to maintain the protection needed when working on hybrid vehicles. </li></ul></ul>
    • 204. TECH TIP <ul><li>Diagnose Bulb Failure </li></ul><ul><ul><li>Halogen bulbs can fail for various reasons. Some causes for halogen bulb failure and their indications are as follows: </li></ul></ul>BACK TO PRESENTATION <ul><ul><li>Gray color. Low voltage to bulb (check for corroded socket or connector) </li></ul></ul><ul><ul><li>White (cloudy) color. Indication of an air leak </li></ul></ul><ul><ul><li>Broken filament. Usually caused by excessive vibration </li></ul></ul><ul><ul><li>Blistered glass. Indication that someone has touched the glass </li></ul></ul>NOTE: Never touch the glass (called the ampoule) of any halogen bulb. The oils from your fingers can cause unequal heating of the glass during operation, leading to a shorter-than-normal service life. <ul><ul><li>Figure 56-18 Handle a halogen bulb by the base to prevent the skin ’s oil from getting on the glass. </li></ul></ul>
    • 205. FREQUENTLY ASKED QUESTION <ul><li>What Is the Difference Between the Temperature of the Light and the Brightness of the Light? </li></ul><ul><ul><li>The temperature of the light indicates the color of the light. The brightness of the light is measured in lumens. A standard 100 watt incandescent light bulb emits about 1,700 lumens. </li></ul></ul>? BACK TO PRESENTATION A typical halogen headlight bulb produces about 2,000 lumens, and a typical HID bulb produces about 2,800 lumens.
    • 206. WARNING <ul><li>Always adhere to all warnings because the high-voltage output of the ballast assembly can cause personal injury or death. </li></ul>BACK TO PRESENTATION
    • 207. TECH TIP <ul><li>Checking a Dome Light Can Be Confusing </li></ul><ul><ul><li>If a technician checks a dome light with a test light, both sides of the bulb will “turn on the light” if the bulb is good. This will be true if the system’s “ground switched” doors are closed and the bulb is good. This confuses many technicians because they do not realize that the ground will not be sensed unless the door is open. </li></ul></ul>BACK TO PRESENTATION
    • 208. FREQUENTLY ASKED QUESTION <ul><li>What Is the Troxler Effect? </li></ul><ul><ul><li>The Troxler effect, also called Troxler fading, is a visual effect where an image remains on the retina of the eye for a short time after the image has been removed. The effect was discovered in 1804 by Igney Paul Vital Troxler (1780–1866), a Swiss physician. </li></ul></ul>? BACK TO PRESENTATION <ul><li>Because of the Troxler effect, headlight glare can remain on the retina of the eye and create a blind spot. At night, this fading away of the bright lights from the vehicle in the rear reflected by the rearview mirror can cause a hazard. </li></ul>
    • 209. TECH TIP <ul><li>The Weirder the Problem, the More Likely It Is a Poor Ground Connection </li></ul><ul><ul><li>Bad grounds are often the cause for feedback or lamps operating at full or partial brilliance. At first the problem looks weird because often the switch for the lights that are on dimly is not even turned on. </li></ul></ul><ul><li>When an electrical device is operating and it lacks a proper ground connection, the current will try to find ground and will often cause other circuits to work. Check all grounds before replacing parts. </li></ul>BACK TO PRESENTATION

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