Am 18
Contents
1. Removing a Headlight Switch Most dash mounted headlight switches can be re moved by first removing the dash panel However to get the dash panel off the headlight switch knob usually has to be removed Some knobs can be re moved by depressing a small clip in a notch in the knob itself Other headlight switch knobs are re moved by depressing a spring loaded release which allows for removal of the entire headlight switch knob and shaft as shown in Figure 18 9 Headlight switches mounted on the steering column are removed as part of the turn signal and wiper switch assembly Many can be easily re moved whereas others require the removal of the steering wheel and so forth See the service infor mation for the exact year and model on which you are working in order to be assured of the correct procedure CIRCUIT BREAKER HEADLIGHT Lighting and Signaling Circuit Operation and Diagnosis 417 E SEALED BEAM HEADLIGHTS Low beam headlights contain two filaments one for low beam and the other for high beam High beam headlights contain only one filament Headlights are standardized so that sealed beam units that can be Q HEAD SWITCH purchased at most auto parts stores can replace i PARK E them Because low beam headlights also contain a miii zgj high beam filament the entire headlight assembly 15 R Y must be replaced if either filament is defective A sealed beam headlight can be tested with an _ 63032. and 700 C It is important never to touch the glass of any halogen bulb with bare fingers because the natural oils of the skin on the glass bulb can cause the bulb to break when it heats during normal operation E HALOGEN SEALED BEAM HEADLIGHTS Halogen sealed beam headlights are brighter and more expensive than normal headlights Because of their extra brightness it is common practice to have Lighting and Signaling Circuit Operation and Diagnosis 419 Diagnose Bulb Failure Halogen bulbs can fail for various reasons Some causes for halogen bulb failure and their indications are as follows e Gray color low voltage to bulb check for corroded socket or connector White cloudy color indication of an air leak Broken filament usually caused by excessive vibration see Figure 18 15 Blistered glass indication that someone has touched the glass NOTE Never touch the glass 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 Figure 18 15 Notice the broken filament in this halogen headlight bulb 420 CHAPTER 18 Figure 18 16 HID Xenon headlights emit a whiter light than halogen headlights and usually look blue only two headlights on at any one time because the candlepower output would exceed the maximum US federal standards if all four halogen headlights were on Therefore before trying to repai
3. t lt 4 BLK 150 c 0325 SEE GROUND DISTRIBUTIO H FLASHER H TAIL STOP TURN 8 BLK CONVENIENCE BRAKE CENTER SWITCH Aranas CLOSED WITH BRAKE PEDAL DEPRESSED 820 C204 8 LT BLU 820 BLK A C324 BLTBLU 820 AL C318 HIGH LEVEL STOP S LIGHT BA C318 8 ox 150 BA C324 1 aux 150 317 8DKBLU 15 Figure 18 7 Typical brake light and taillight circuit showing the brake switch and all of the related circuit components built into a ceramic holder that is designed to insu late the rest of the switch from the heat and allow heat to escape Continual driving with the dash lights dimmed can result in the headlight switch knob getting hot to the touch This is normal and the best prevention is to increase the brightness of the dash lights to reduce the amount of heat generated in the switch The headlight switch also contains a built in circuit breaker that will rapidly turn the headlights on and off in the event of a short circuit This prevents a total loss of headlights If the head lights are rapidly flashing on and off check the en tire headlight circuit for possible shorts The circuit breaker controls only the headlights The other lights controlled by the headlight switch taillights dash lights and parking lights are fused separately Flashing headlights may also be caused by a failure in the built in circuit breaker requiring replacement of the switch assembly
4. Lighting and Signaling Circuit Operation and Diagnosis OBJECTIVES After studying Chapter 18 the reader should be able to Prepare for ASE Electrical Electronic Systems A6 certification test content area E Lighting System Diagnosis and Repair 2 Determine which replacement bulb to use on a given vehicle 3 Describe how turn signals work 4 Use a bulb chart 5 Discuss troubleshooting procedures for lighting and signaling circuits i he lighting and signaling circuits represent two of the most frequently serviced automotive electrical areas E LIGHTING Exterior lighting is controlled by the headlight switch which is connected directly to the battery on most vehicles Therefore if lights are left on it can drain the battery Most headlight switches contain a built in circuit breaker If excessive current flows through the headlight circuit the circuit breaker will momentarily open the circuit then close it again The result is headlights that flicker on and off rapidly NOTE This flickering on and off is misunderstood by many drivers and technicians Because the flickering is rapid many people believe that the problem is caused by a loose headlight or by a defective voltage regulator This feature allows the headlights to function as a safety measure in spite of current overload The headlight switch controls the following lights on most vehicles 1 Headlights 2 Taillights
5. 3 Side marker lights 4 Front parking lights 5 Dash lights 6 Interior dome light s NOTE Because these lights can easily drain the bat tery if accidentally left on many newer vehicles control these lights through the vehicle s computer The com puter keeps track of the time the lights are on and can turn them off if the time is excessive The computer can control either the power side or the ground side of the circuit B BULB NUMBERS The number used on automotive bulbs is called the bulb trade number as recorded with the American National Standards Institute ANSI and the number is the same regardless of the manufacturer Amber color bulbs that use natural amber glass are indicated 4ll 412 CHAPTER 18 with an NA for natural amber at the end of the num ber for example 1157NA A less expensive amber bulb that uses painted glass is labeled A for amber for example 1157A See Figure 18 1 aa WURTH sans 3157 3157NA Lt E 7 PUSS 7NA Figure 18 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 for use with clear turn signal lenses Figure 18 2 This single filament bulb is being tested with a digital multimeter set to read resistance in ohms The reading of 1 3 ohms is the resistance of the bulb when cold As soon as current flows through the filament the resistance increases
6. ward along the power side of the circuit in search of a return path ground to the battery this reverse flow is called feedback or reverse bias current flow Feedback can cause other lights or gauges to work that should not be working Lighting and Signaling Circuit Operation and Diagnosis 425 Feedback Example 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 The front parking light bulb is a dual fila ment one filament for the parking light dim and one filament for the turn signal operation bright A corroded socket did not provide a good enough ground to conduct all current required to light the dim filament of the bulb The two filaments of the bulb share the same ground connection and are electrically connected 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 The turn signal filament is electrically connected to the dash indicator light therefore the reversed current on its path toward ground could light the turn signal indicator light Cleaning or re placing the socket usually solves the problem if the ground wire for the socket is making a secure chas sis ground connection 426 CHAPTER 18 One headlight e Poor ground dim connection
7. 18 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 TURN DIRECTIONAL SIGNALS A turn signal flasher unit is a metal or plastic can containing a switch that opens and closes the turn signal circuit See Figure 18 19 This turn signal flasher unit is usually installed in a metal clip at tached to the dash panel to allow the clicking noise of the flasher to be heard by the driver The turn sig nal flasher is designed to transmit the current to light the front and rear bulbs on only one side at a time The U S Department of Transportation DOT regulation requires that the driver be alerted when a turn signal bulb is not working This is achieved by using a series type flasher unit The flasher unit re Figure 18 19 Two styles of two prong flashers quires current flow through two bulbs one in the front and one in the rear in order to flash If one bulb burns out the current flow through only one bulb is not sufficient to make the unit flash it will be a unit may become corroded and pitted requiring steady light These turn signal units are often called higher voltage to operate To restore normal opera DOT flashers When the turn signal flasher unit is tion replace the turn signal flasher unit Other com old the lights w
8. fies sel l AZARD k CONTACT l LIGHTS DAL i l HEADLIGHT E E a CLOSED IN I MODULE SEARA ee 1 SWITCH I ME I OPES OFE 1 ASSEMBLY PARK b ON ENABLE d 7 d i ES l I I AS I X h CONTACT l I l CLOSED l I 1 CONTACT IN NGHT l l 1 CLOSED IN MODE l C1 I DAY MODE FRONTATAIL l DRL HEAD LIGHTS ON l 4 LIGHTS ON ENABLE ENABLE Oa sn ee a a d 11 E Y Sto AP om 1DK I P101 BLU WHT 593 1 YEL TA 2 3 W Cc 101 1LTGRN 11 1TAN s115 11 Coe ei oas ama ma e ee a m r IB c ee I ay Composite I A Z I COMPOSITE Heap HEAD e I HEAD I Gaur I HEADLIGHT LIGHT I HEADLIGHT r m ASSEMBLY l O eo _ e e e o G e n o n a l MM Jaina mi RSC 1 DK BLU WHT 593 ERER i 1 BLK 151 8 A C101 IC 101 i 2BLK 151 S22 ESS A ee ee ee 2 G115 Figure 18 17 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 421 422 CHAPTER 18 Lights Lights switch switch Off On Dimmer 4 switch High Common Low __ N lead High headlights Common 3 Dimmer switch Ground Positive switching Negative switching Figure 18
9. ohmmeter A good bulb should indicate low ohms be MULTIFUNCTION g STEERING DIMMER tween the ground terminal and both power side hot COLUMN SWITCH terminals If either the high beam or the low beam panyen f HI l filament is burned out the ohmmeter will indicate 4 HIGH BEAM INDICATOR RELEASE BUTTON infinity OL See Figure 18 10 E HEADLIGHT AIMING According to U S federal law all headlights regard less of shape must be able to be aimed using head light aiming equipment See Figures 18 11 through 18 13 Figure 18 8 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 18 9 To remove the headlight switch from a vehicle that uses a knob and shaft a release button has to be pushed to release the shaft After the knob and shaft assembly has been removed then the retaining nut can be removed from the headlight switch so it can be removed from the dash 418 CHAPTER 18 2 Lamp system and circular 4 lamp system TOP ADJUSTING ms Wi SIDE ADJUSTING SCREW Low Common High Rectangular 4 lamp system AIMING UNIT Common Low 3 Figure 18 11 All vehicles sold in the United States must High have provision for the use of mechanical aiming devices Even the
10. to the left side lights c A defective open parking light or taillight bulb on the left side d A defective open parking light or taillight bulb on the right side A defective taillight or front park light bulb could cause a The turn signal indicator on the dash to light when the lights are turned on b The dash lights to come on when the brake lights are on c The lights on warning chime to sound if the brake pedal is depressed d All of the above A defective brake switch could prevent proper operation ofthe _____ __ _ _ a Cruise control b ABS brakes c Shift interlock d All of the above
11. 12 2 continued DIAGNOSTIC STORY Weird Problem Easy Solution A General Motors minivan had the following electrical problems The turn signals flash rapidly on the left side With the ignition key off the lights on warning chime sounds if the brake pedal is depressed When the brake pedal is depressed the dome light comes on All of these problems were caused by just one de fective 2057 dual filament bulb shown in Figure 18 5 Apparently the two filaments were electrically connected through the corrosion observed between the terminals of the bulb This caused the electrical current to feed back from the brake light filament into the taillight circuit causing all the problems See Figure 8 6 for another ex ample of a weird bulb problem Figure 18 5 Corrosion caused the two terminals of this dual filament bulb to be electrically connected E BRAKE LIGHTS Brake lights use the high intensity filament of a double filament bulb The lower intensity filament is for the taillights The brake light switch is a nor mally open N O switch but is closed when the driver depresses the brake pedal Since 1986 all ve hicles sold in the United States have a third brake lig
12. 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 a 2057 and are shown separately to help explain how the side marker light works on many vehicles TECH TIP Service Manual Diagnosis It used to be that if a technician could see the schematic of the circuit being diagnosed then the problem could be corrected From the schematic or wiring diagram the technician could see where voltage should be at various parts of the circuit Not any more Many of today s vehi cles use a computer to control almost everything includ ing interior lights The old switches in the door jamb sim ply signal the computer that a door has been opened The computer controls the lighting to help control against ac cidental battery drain For example in the event that the vehicle door has been left open the computer can open the circuit and prevent a dead battery The schematic rarely shows exactly how the circuit works However most service manuals walk you through the diagnosis With a service manual or serv ice disk if on compact disk with read only memory CD ROM the technician is not lost Always follow the pro cedures exactly Even if the service procedure sounds long and involved the procedure will lead you to the correct diagnosis Dne Figure 18 21 A typical courtesy light door jamb switch Newer vehicles use the door switch as
13. 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 The trade number also identifies the size shape number of filaments and amount of light produced The amount of light produced is measured in candle power For example the candlepower of a 1156 bulb commonly used for backup lights is 32 A 194 bulb commonly used for dash or side marker lights is rated at only 2 candlepower The amount of light produced by a bulb is determined by the resistance of the filament wire which also affects the amount of current in amperes required by the bulb See Fig ures 18 2 and 18 3 It is important that the correct trade number of bulb always be used for replacement to prevent cir cuit or component damage The correct replacement bulb for your vehicle is usually listed in the owner s manual or service manual See Figure 18 and the bulb chart Typical Automotive Light Bulbs Trade Design Design Watts Number Volts Amperes P I1XE 37 14 0 0 09 1 3 37E 14 0 0 09 51 7 5 0 22 continued Figure 18 3 Close up of a dual filament double filament bulb 1157 that failed Notice that one filament top broke from its m
14. an input to the vehicle computer and the computer turns on or off the interior lights 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 E FIBER OPTICS Fiber optics is the transmission of light through spe cial plastic polymethyl methacrylate that keeps the light rays parallel even if the plastic is tied in a knot These strands of plastic are commonly used in auto motive applications as indicators for the driver that certain lights are functioning For example some ve hicles are equipped with fender mounted units that light whenever the lights or turn signals are operat ing Plastic fiber optic strands which often look like standard electrical wire 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 Fiber optic strands can also be run like wires to in dicate the operation of all lights on the dash or con sole Fiber optic strands are also commonly used to light ashtrays outside door locks and other areas where a small amount of light is required The source of the light can be any normally operating light bulb A special bulb clip is usually used to retain the fiber optic plastic tube near the bulb E FEEDBACK When current that lacks a good ground goes back
15. educed intensity whenever the engine is running or the vehicle is moving High intensity discharge HID headlights are brighter and have a blue tint One defective turn signal bulb causes the turn signal on the affected side to stop blinking flashing E REVIEW QUESTIONS Explain why the exact same trade number of bulb should be used as a replacement Explain why you should not touch a halogen bulb with your fingers Describe how to diagnose a turn signal operating problem Discuss how to aim headlights on a vehicle equipped with aerodynamic style headlights i ASE CERTIFICATION TYPE QUESTIONS 1 Technician A says that the bulb trade number is the same for all bulbs of the same size Techni cian B says that a dual filament bulb has differ ent candlepower ratings for each filament Which technician is correct a Technician A only b Technician B only c Both Technicians A and B d Neither Technician A nor B Two technicians are discussing flasher units Technician A says that a DOT approved flasher unit should be used only for turn signals Techni cian B says that a variable load flasher will func tion for turn signal usage although it will not warn the driver if a bulb burns out Which tech nician is correct a Technician A only b Technician B only c Both Technicians A and B d Neither Technician A nor B Interior overhead lights dome lights are oper ated by doo
16. em for a different trade number A fleet duty designa tion represents some increase in durability and a heavy duty designation identifies the most severe service bulb TECH TIP Heavy Duty Automotive Bulbs Regular Fleet Duty Heavy Duty 182 1445 or 53X 1895 158 161 1003 1004 1034 1157 1034A 157NA 1 157A 1073 1156 1141 1889 1891 1893 4000 4040 6014 6015 Therefore if the specification for your vehicle gives a trade number listed under the regular heading you can safely switch to the trade number of bulb listed under the fleet duty or heavy duty heading For best operation of turn signals and consistent brightness of bulbs the switch of trade numbers should include all similar bulbs of the type being replaced time A circuit breaker is built into most headlight switches to protect the headlight circuit See Figure 18 8 The interior dash lights can be dimmed manu ally by rotating the headlight switch knob which controls a variable resistor called a rheostat built into the headlight switch The rheostat drops the voltage sent to the dash lights Whenever there is a voltage drop increased resistance there is heat A coiled resistance wire is 416 CHAPTER 18 r SEE POWER DISTRIBUTION a 1DKBLK 75 msnasnnemasnnmanassan Ero TAIL STOP TURN LIGHTS STOP TURN 150 a SEE GROUND m DISTRIBUTION gt BLK 8 BLK NT SAE AESTS TSE
17. halogen bulb units with plastic or glass lenses an ann have locating points and adjustment screws Figure 18 10 Typical headlight socket connections Some vehicles may be different The high and low beam connections must be determined by visual inspection PAINTED REFERENCE LINE 12 FEET 3 6 m MINIMUM i DISTANCE BETWEEN HEADLAMPS ADJUSTABLE VERTICAL TAPES CENTER LINE OF SCREEN ADJUSTABLE HORIZONTAL TAPES DIAGRAM OF LIGHT SCREEN ON SHOP FLOOR VERTICAL VEHICLE VERTICAL VERTICAL CENTERLINE CENTERLINE CENTERLINE AHEAD OF LEFT AHEAD OF RIGHT AHEAD OF LEFT HEADLAMP HEADLAMP HEADLAMP os A HEIGHT OF eae LAMP CENTERS A HIGH INTENSITY HIGH HIGH INTENSITY AREA INTENSITY AREA AREA Figure 18 12 Typical headlight aiming diagram as found in a service manual VERTICAL a CENTERLINE AHEAD OF RIGHT HEADLAMP HEIGHT OF LAMP CENTERS HIGH INTENSITY AREA Figure 18 13 Many composite headlights have a built in bubble level to make aiming easy and accurate Figure 18 14 A typical composite headlamp assembly The lens housing and bulb sockets are usually included as a complete assembly E COMPOSITE HEADLIGHTS Composite headlights are constructed using a re placeable bulb and a fixed lens cover that is part of the vehicle See Figure 18 14 The replaceable bulbs are usually bright halogen bulbs Halogen bulbs get very hot during operation between 500 and 1300 F 260
18. ht commonly referred to as the center high mounted stop light CHMSL The brake switch Figure 18 6 Often the best diagnosis is a thorough visual inspection This bulb was found to be filled with water causing weird problems TECH TIP No Cruise Control Check the Third Brake Light A common cause of an inoperative cruise control especially on General Motors vehicles is a burned out bulb in the third stop light The cruise control uses the filaments of the third brake bulb as a ground and shuts off the cruise if the bulbs are burned out open See Figure 8 7 is also used as an input switch signal for the fol lowing 1 Cruise control deactivates when the brake pedal is depressed 2 Antilock brakes ABS 3 Brake shift interlock prevents shifting from park position unless the brake pedal is depressed amp HEADLIGHT SWITCHES The headlight switch operates the exterior and inte rior lights of most vehicles The headlight switch is connected directly to the battery through a fusible link and has continuous power or is hot all the Lighting and Signaling Circuit Operation and Diagnosis 415 Many automotive bulbs have the same operating param eters same wattage voltage amperage and candle power yet have different trade numbers Some numbers are for standard duty whereas others have heavier fila ment wire or additional filament support which qualifies th
19. ight switch knob fully counterclockwise left or by operating switches located in the door jambs of the vehicle doors and or near the dome light There are two types of circuits commonly used for these interior lights Most manu facturers except Ford use the door switches to ground the courtesy light circuit See Figure 18 21 Many Ford vehicles use the door switches to open and close the power side of the circuit Many newer vehicles operate the interior lights through the vehicle computer or through an electronic module Because the exact wiring and operation of these units differ consult the service literature for the exact model on which you are working BE ILLUMINATED ENTRY Some vehicles are equipped with illuminated entry whereby the interior lights are turned on for a given amount of time whenever the outside door handle is operated while the doors are locked Most vehicles equipped with illuminated entry also light the exte rior door keyhole Some vehicles equipped with body computers use the door handle electrical switch of the illuminated entry circuit to wake up the power supply for the body computer 424 CHAPTER 18 Fusible Ignition Flasher Turn ay k switch 20 A unit nigra Headlight Ba ee ee switc switch O L R Y Left turn Dash Side marker s m gt light Park light Figure 18 20 The side marker light goes out whenever there is voltage at both point X and Y
20. ill flash more slowly both sides af mon turn signal problems and possible solutions in fected equally The contact points inside the flasher clude the following Possible Causes and Problem or Solutions 1 Slow flashing on both sides equally 1 Replace the worn flasher unit Check the battery and the charging voltage to be certain that the charging circuit and battery are supplying high enough voltage for proper operation of the turn signals 2 Slow or no flashing 2 Replace the defective on one side only bulb or clean poor connections on the front or rear bulbs on the side that does not work 3 Turn signals not 3 The most likely cause is a flashing on defective flasher unit in either side which case replacement will be necessary However defective bulbs or connections on both sides could also be the cause Most turn signal flasher units are mounted ina metal clip that is attached to the dash The dash panel acts as a sounding board increasing the sound of the flasher unit Most four way hazard flasher units are plugged into the fuse panel Some two way turn signal flasher units are also plugged into the fuse panel How do you know for sure where the flasher unit is located With both the turn sig nal and the ignition on listen and or feel for the clicking of the flasher unit Some service manuals also give general locations for the placement of flasher units E HAZARD FLASHERS Hazard flasher unit
21. on body One headlight out dim or bright e Burned out headlight filament Check the headlight with an ohmmeter There should be a low ohm reading between the power side connection and the ground terminal of the bulb Both high and low beam headlights out e Burned out bulbs Check for voltage at the wiring connector to the headlights possible open circuit to the headlights or open defective dimmer switch All headlights inoperative e Burned out filaments in all headlights Check for proper charging system voltage e Defective dimmer switch L e Defective headlight switch Slow turn signal operation e Defective flasher unit e High resistance in sockets or ground wire connections e Incorrect bulb numbers Turn signals operating on one side only Interior light s inoperative e Burned out bulb on affected side e Poor ground connection or defective socket on affected side e Incorrect bulb number on affected side e Burned out bulb s e Open in the power side circuit blown fuse e Open in door jamb switch es Interior lights on all the time e Shorted door jamb switch e Headlight switch turned fully counterclockwise Hazard warning lights inoperative Hazard warning lights blinking too rapidly Brake lights inoperative Ta Defective brake switch e Defective turn signal switch e Burned out brake light bulbs e Open circuit or poor ground connection e Defective hazard fla
22. ounting and melted onto the lower filament This bulb caused the dash lights to come on whenever the brakes were applied Lighting and Signaling Circuit Operation and Diagnosis 413 Trade Design Design Watts Number Volts Amperes P IxE 561 12 8 0 97 12 4 562 13 5 0 74 10 0 563 13 5 0 52 7 0 631 14 0 0 63 8 8 DOUBLE CONTACT SINGLE CONTACT 880 12 8 2 10 27 0 1157 2057 BULBS 1156 BULBS 128 210 270 13 0 0 69 9 0 12 8 1 00 12 8 12 8 0 94 12 0 o 128 0 94 12 0 heia 12 8 1 80 0 59 23 0 7 6 12 8 1 80 23 0 Figure 18 4 Bulbs 1157 or 2057 are typically used for taillight and front parking lights These bulbs contain both a low intensity filament for taillights or parking lights and a high intensity filament for brake lights and turn signals Trade Design Design Watts Number Volts Amperes P IXE 63 7 0 0 63 4 4 67 13 5 0 59 8 0 68 13 5 0 59 8 0 70 14 0 0 15 2 1 1154 2 63 0 75 16 8 4 5 1156 2 10 26 9 1157 2 10 0 59 26 9 7 6 1157A 2 10 0 59 26 9 7 6 1157NA 2 10 0 59 26 9 7 6 1176 1 34 0 59 17 2 7 6 3 00 37 5 3 00 37 5 1445 0 13 1 9 1816 0 33 4 3 1889 0 27 3 8 1891 0 24 3 4 1892 0 12 nee 1893 0 33 46 1895 0 27 3 8 2033 0 22 3 0 2057 2 10 0 48 26 9 6 1 2057NA 2 10 0 48 26 9 6 1 2322 1 0 16 2 0 2721 0 10 TL2 2821 4 00 3 0 2825 0 42 5 0 0 16 2 1 1 10 12 8 168 192 194 194E 1 194NA 209 211 2 2
23. r jamb switches that a Complete the power side of the circuit b Complete the ground side of the circuit c Move the bulb s into contact with the power and ground d Hither a or b depending on application 10 Electrical feedback is usually a result of a Too high a voltage in a circuit b Too much current in amperes in a circuit c Lack of a proper ground d Both a and b Which bulb is brightest see the bulb table a 194 b 168 c 194NA d 57 Ifa 1157 bulb were to be installed in a left front parking brake socket instead of a 2057 bulb what would be the most likely result a The left turn signal would flash faster b The left turn signal would flash slower c The left parking light would be slightly brighter d The left parking light would be slightly dimmer A technician replaced a 1157NA with a 1157A bulb Which is the most likely result a The bulb is brighter because the 1157A candlepower is higher b The amber color of the bulb is a different shade c The bulb is dimmer because the 1157A candlepower is lower d Both b and c A customer complained that every time he turned on his vehicle s lights the left side turn signal indicator light on the dash remained on The most likely causeis_ s a A poor ground to the parking light or taillight bulb on the left side b A poor ground to the parking light or taillight bulb on the right side causing current to flow
24. r the prob lem that only two of the four lamps are on check with the owner s manual or the shop manual for proper operation E HIGH INTENSITY DISCHARGE HEADLIGHTS High intensity discharge HID headlights pro duce a distinctive blue white light that is crisper clearer and brighter than light produced by a halo gen headlight Unlike a halogen bulb the HID bulb has no filament It creates light from an electrical discharge between two electrodes in a gas filled arc tube It produces twice the light with less electrical input than conventional halogen bulbs The HID lighting system consists of the dis charge arc source igniter ballast and headlight as sembly The two electrodes are contained in a tiny quartz capsule filled with xenon gas mercury and metal halide salts The lights and support electronics are expensive but they should last the life of the ve hicle unless physically damaged See Figure 18 16 The temperature of daylight compared to various types of bulbs includes E Daylight 5400 K HID 4100 K Halogen 3200 K E Incandescent tungsten 2800 K E DAYTIME RUNNING LIGHTS Daytime running lights DRLs involve operating front parking lights or the headlights usually at re duced current and voltage whenever the vehicle is running Canada has required daytime running lights on all new vehicles since 1990 DRLs have re duced accidents where used Daytime running lights primarily u
25. s are usually plugged into the fuse panel and are designed to flash four or more bulbs safely and at the same flashing speed regardless of the number of bulbs used in the lighting circuit Therefore if trailer lights are connected to the taillights the flasher unit for the four way hazard flasher should be used in place of the standard turn signal flasher However the regular DOT turn signal flasher cannot be used for the four way haz ard flashers The result would be the very rapid Lighting and Signaling Circuit Operation and Diagnosis 423 Frequently Asked Question Bee Why Does the Side Marker Light Alternately Flash 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 their vehicle while actually it is normal operation The side marker light goes out whenever 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 18 20 Normally the side marker light gets its ground through the turn signal bulb flashing of the hazard flasher and damage to the flasher itself E COURTESY LIGHTS Courtesy lights is a generic term primarily used for interior lights including overhead dome and under the dash courtesy lights These interior lights can be operated by rotating the headl
26. se a control module that turns on either the low or high beam lamps The lights on some vehicles come on when ever the engine starts Some vehicles will turn on the lamps when the engine is running but delay their operation until a signal from the vehicle speed sen sor indicates that the vehicle is moving To avoid having the lights on during servicing some systems will turn off the headlights whenever the parking brake is applied Others will only light the headlights when the vehicle is in a drive gear See Figure 18 17 E DIMMER SWITCHES The headlight switch controls the power or hot side of the headlight circuit The current is then sent to the dimmer switch which allows current to flow to either the high beam or the low beam filament of the headlight bulb as shown in Figure 18 18 An indica tor light lights on the dash whenever the bright lights are selected The dimmer switch can be either foot operated on the floor or hand operated on the steering column The popular steering column switches are actually attached to the outside of the steering column on most vehicles and are spring loaded To replace most of these types of dimmer switches the steering col umn needs to be lowered slightly to gain access to the switch itself which is also adjustable for proper lever operation HDLP CIRCUIT BREAKER 640 DAYTIME m lt e m e e e e l l I TURN RUNNING i
27. sher unit e Open in hazard circuit e Incorrect flasher unit e Shorted wiring to front or rear lights e Incorrect bulb numbers TAIL LIGHT FAULT INDICATOR amp Ea rn The driver noticed that the taillight fault 2 A visual inspection at the rear of the vehicle indicator icon on the dash was on any time the lights niac that the right rear taillight bulb did not light were on Removing a few screws from the plastic cover revealed the taillight assembly P18 3 The bulb socket is removed from the taillight P 4 The bulb is removed from the socket by gently assembly by gently twisting the base of the bulb grasping the bulb and pulling the bulb straight out of counterclockwise the socket Many bulbs require that you rotate the bulb 90 1 4 turn to release the retaining nibs P18 5 The new 7443 replacement bulb is being i 6 The replacement bulb is inserted into the tail checked with an ohmmeter to be sure that it is OK light socket and the lights are turned on to verify before installing it in the vehicle proper operation before putting the components back together The dash warning light was also off after the bulb was replaced 428 CHAPTER 18 E SUMMARY 1 2 Automotive bulbs are identified by trade numbers The trade number is the same regardless of manufac turer for the exact same bulb specification Daytime running lights DRLs light the headlights usually at r
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