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Lighting and Accesories Circuit

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Lighting system Summary The lighting system allows the driver to see when driving at night or in poor visibility conditions, and to signal to other drivers. Lighting systems improve visibility at night, and make a vehicle visible to other road-users. A lighting switch operates tail-lights, park lights, and headlights to allow the driver to see ahead. A dip switch allows the driver to change the beams from high to low, or vice-versa, as required. Stop-lights operate when the brake pedal is depressed.
Transcript

Lighting system

SummaryThe lighting system allows the driver to see when driving at night or in poor visibility conditions, and to signal to other drivers.

Lighting systems improve visibility at night, and make a vehicle visible to other road-users.A lighting switch operates tail-lights, park lights, and headlights to allow the driver to see ahead. A dip switch allows the driver to change the beams from high to low, or vice-versa, as required.Stop-lights operate when the brake pedal is depressed.Turn-signals alert other drivers of a change in direction, and are mounted so they can be seen from the front, rear and sides of the automobile.An emergency flasher system operates both front and rear turn-signals at the same time.Other circuits operate courtesy, or convenience lights, reversing lights, and fault indicators. Lamps/light bulbs

SummaryMost lamps or light bulbs consist of a fine coil of tungsten wire, called a filament, enclosed in a clear glass envelope from which all air has been removed. .

Modern vehicles use many different kinds and sizes of lamps, also known in some places as light bulbs, or light globes.Incandescent lamps'Incandescent' lamps all consist of one or more filaments which heat up until they glow. The filament material doesn't burn because most of the air in the bulb has been replaced by inert gases that stop combustion occurring.The power in watts is often marked on the lamp. The power in watts being consumed by the lamp is found by multiplying the voltage to the lamp by the current flowing through it.Halogen lampsHalogen lamps are filled with a halogen gas such as bromine or iodine. These have a much longer life, and are generally brighter and produce more light per unit of power consumed, but they are very hot in use. They are consequently manufactured from highly heat resistant materials and the bulbs must be handled carefully because they are sensitive and can be damaged even by residue from fingerprintsOther lamp typesConventional incandescent lamps are being replaced in many applications by other more efficient types of lights, such as fluorescent lights, high-intensity discharge (HID) lights, and light-emitting diodes (LED). Lamp/light bulb information

SummaryAll lamps or light bulbs have letters or numbers which indicate the power consumed by the bulb in operation and the nominal operating voltage.

All lamps or light bulbs have letters and numbers stamped on them which indicate the power consumed by bulb operation at the nominal operating voltage.For instance, in a 12V / 21W bulb the filament will consume 21 watts of power when 12 volts is applied across the filament.While the wattage is not necessarily an indication of light output, it can be generally assumed that, for similar types of lamps, the higher the wattage the greater the light output will be. LED lighting

SummaryLight Emitting Diodes, or LEDs, are being increasingly used in automotive lighting applications, because they operate instantly, are more reliable, and last longer.

Light Emitting Diodes, or LEDs, have been used for some time in various automotive applications such as warning indicators and alphanumeric displays. More recent developments in LED technology have seen the production of a wider range of colors, and LEDs that are brighter than previous types.It is now possible to get bright red, green, blue, yellow and clear or white light LEDs. This has made it possible to use LEDs for many new applications, such as more general lighting applications. For example LEDs can now be used for stoplights, indicators and interior lighting on vehicles.One of the advantages of LEDs is that they turn on instantly. This is particularly useful in brake lights as they can reduce the braking response time by 2/10th of a second. This translates to an extra 16 feet or 5 meters of stopping distance at highway speeds. LEDs also have better visibility in poor weather and they can last up to 100 times longer, reducing the cost of servicing.LEDs can be specifically designed for LED lighting and also as LED replacement bulbs for more traditional bulb holders.For automotive applications a number of LEDs are grouped together to provide the amount of light required for the application. Additionally LED light lenses are specifically designed to get the most out of the available light.An LED is like a normal diode and only passes current flow in one direction. This means they are polarity conscious. When an LED is forward biased, current flows through it and it emits light. So it is essential that when the LED is coupled to an electricity supply, it must be done in the correct polarity in order for the lights to work. A typical LED has a voltage drop of 1.2 volts across it when it is forward biased and emitting light.When used in automotive lighting, many LEDs are required to give off the required amount of light. To do this they are usually connected in groups called series strings. A number of series strings are then connected in parallel until the necessary number of LEDs are connected to give off the required amount of light.LEDs work best when the voltage to them and the current flow through remains constant at a preset level. There are two main ways to achieve this; the first is via a resistor. The second and more preferred way is through the use of a voltage regulation circuit.Some LED lights are multi-voltage, this means they can work on both 12 and 24-volt systems. These are normally used in aftermarket products, which are able to be fitted to a wide range of vehicles. Stop lights

SummaryStop lights are red lights fitted to the rear of the vehicle which are activated whenever the drive operates the foot brake to slow or stop the vehicle.

Stop lights are red lights fitted to the rear of the vehicle. They are usually incorporated in the taillight cluster although many vehicles have a higher additional stop light mounted on top of the boot lid or on the rear window called a high-level stop lamp.The stop lights are activated whenever the driver operates the foot brake to slow or to stop the vehicle.The circuit consists of: the battery, fusible links and fuses, a stop light switch, stop light bulbs, wiring to connect the components, and the ground circuit to return current from the filaments to the battery.When the operator of the vehicle depresses the brake pedal, a switch mounted on the pedal support is closed. This allows electrical current to flow from the battery through the fuse, through the switch, to the brake light filaments and to return to the battery by the ground system.When the driver releases the pedal, it returns to the rest position and open circuits the stoplight circuit. The flow of electrical current stops and the brake lamps are extinguished. Reverse lights

SummaryReversing lights are white lights fitted to the rear of a vehicle. They provide vision behind the vehicle and warn other drivers that the vehicle will move backwards.

The reversing lights are white lights fitted to the rear of a vehicle. They provide the driver with vision behind the vehicle at night, and also alert other drivers to the fact that the vehicle is to be reversed.The circuit consists of: the battery fuses and fusible links the ignition switch, the reversing light switch on the transmission, reversing light filaments, wiring to connect the components, and the ground circuit to allow current to return to the battery through the vehicle frame.When the ignition switch is on and the vehicle is placed in reverse gear current flows from the battery, through the ignition switch, to the closed reversing light switch on the transmission.Electrical current flows across the closed switch to the reversing lights, and then returns to the battery by the earth return system. Indicators

SummaryIndicators are amber lights located at the corners of the vehicle. They are pulsing lights that warn other road users of an intended change in direction.

Indicators are amber lights located on the extreme corners of the vehicle. A column mounted switch, operated by the driver, directs a pulsing current to the indicator lights on one side of the vehicle or the other. These pulsing lights warn other road users of the vehicles intended change of direction.Once activated they continue until the switch is cancelled either by the operator or by a cancelling mechanism in the switch. The cancelling mechanism operates after a turn has been completed and the steering wheel is returned to the straight ahead position.The circuit consists of: the battery fusible links and fuses, the ignition switch, the flasher unit, a three position switch used as the direction indicator switch, the lights at the front and rear of the vehicle, pilot lights mounted in the instrument cluster to indicate to the driver which way the switch has been operated, wiring to connect all of the components, and the ground circuit to return the electrical current to the battery.If the indicator switch is turned to indicate a right-hand turn, current from the battery flows through the fusible link to the ignition switch, where it is directed through a fuse to the flasher unit.The flasher unit uses a timing circuit to pulse the current flowing out of the flasher unit 60 to 120 times per minute. This pulsing current is directed through the indicator switch to the right-hand indicator lights at the front and rear of the vehicle, causing the lamps to flash on and off. A pilot light on the instrument cluster also pulsates. The operation of the flasher unit also produces a clicking sound to warn the driver that the indicators are in operation.When the indicator switch is returned to the off or central position, no current flows through the flasher unit so the timer circuit is switched off.When the indicator switch is turned in the opposite direction, it directs the pulsing current to the left-hand lights at the front and rear of the vehicle as well as the left hand pilot light on the instrument cluster.Most vehicles are equipped with hazard warning lights. This circuit is similar to the indicator lights except that it simultaneously causes a pulsing in all exterior indicator lights and both pilot lights on the instrument panel .These can warn other road users that a hazardous condition exists, or that the vehicle is standing or parked in a dangerous position on the side of the road. Headlights

SummaryIn headlight bulbs the main beam filament is positioned at the focal point of the reflector, and the dip beam filament is placed above and slightly to one side.

Headlights or headlamps are built in to the front of a vehicle, to illuminate the road ahead of the vehicle when driving at night, or in other conditions of reduced visibility.In headlights two filaments are necessary to provide for a main and a dip beam function. These must be positioned correctly in relation to the highly polished reflector. This is called focusing and is carried out during manufacture.The main or high beam filament is positioned at the focal point of the reflector to project the maximum amount of light forward and parallel to the reflector axis. This light is then shaped by the lens which is made up of many small glass prisms fused together. These prisms bend the light horizontally and vertically to achieve the desired pattern for road illumination.The dip or low beam is placed above and slightly to one side of the main filament. Mounting the dip filament in this position produces a beam of light that is projected downwards and towards the kerb side.With this arrangement the main filament produces the best possible light output while the dip filament gives a downward and dispersed beam which should not dazzle oncoming drivers.A semi-sealed beam headlight uses a replaceable bulb with a pre-focus collar. The collar locates the bulb in the headlight and also controls the correct positioning of the filaments.A sealed beam headlight has a highly polished aluminized glass reflector which is then fused to the optically designed lens. This forms a completely sealed unit which has the filaments accurately positioned in relation to the reflector. When a filament fails in a sealed beam light, the whole unit must be replaced.Some headlight bulbs have a partial shield below the dip filament. This shield stops light from the filament striking the lower part of the reflector. The shield provides the primary shape of the dip beam. The final shaping of the beam is carried out by small cylindrical shaped prisms in the headlight lens. This provides a dipped beam that is asymmetrical. High intensity discharge (HID) lights

SummaryHigh Intensity Discharge or HID lights provide better illumination than other types of lights.

High Intensity Discharge or HID lights can be recognized by their extremely bright white or bluish light. They provide better illumination than other types of lights.HID lights improve visibility. Drivers using HID lights are able to see the road ahead for approximately 300 feet or 100 meters, compared to about 200 feet or 60 meters for a halogen system.In comparison with halogen lights, HID headlights can be up to 3 times brighter, are more efficient in converting electrical energy into light energy, have a longer service life, and the light color is whiter or closer to daylight.They operate on a gas discharge bulb system and consist of a light, bulb, ballast and special high voltage circuitry. HID headlights systems do not use a filament in the bulb. They have the inert gas Xenon inside the bulb, with two electrodes that have an air gap between them in a glass tube. A high voltage is applied between the electrodes. This causes an arc to form, which vaporizes the gases and solids so they emit a bright light. The voltage required to strike and maintain the arc is very high - typically up to 20, 000 volts. Driving lights

SummaryDriving lights are used to supplement vehicle headlight systems.

Driving lights are used to supplement vehicle headlight systems. The driving lights are fitted to the front of the vehicle and provide higher intensity illumination over longer distances than standard headlight systems. Vehicle design rules and regulations specify the limitations in relation to the positioning of driving lights. It is essential that the local regulations are adhered to when fitting or adjusting driving lights.There are many types of driving lights available. They come in different sizes, different shapes and varying lamp/light bulb wattage. In some instances a single driving light can be fitted to suit particular applications, but they are normally fitted in pairs.Most driving lights use quartz halogen bulbs in the 55 watts to 120 watts range. The quality of the reflector is extremely important in driving lights to get optimum performance.Driving lights are wired so that they only operate when high beam is operating. This safety feature ensures that driving lights turn off when the headlights are dipped from high to low beam, thus ensuring oncoming traffic does not get accidentally blinded by excessive light.A relay and circuit breaker should always be used for driving lights for safety reasons. Fog lights

SummaryFog lights are used with other vehicle lighting in poor weather such as thick fog, driving rain or blowing snow.

Fog lights are used with other vehicle lighting in poor weather such as thick fog, driving rain or blowing snow. Because fog is made up of water droplets suspended in the air it can reflect headlights back into your eyes at night. In such conditions, fog lights can help drivers see further ahead and illuminate the roads edges at reasonable speeds and are used with park lights instead of headlights.Most fog lights have yellow colored reflectors, although more recently white fog lights are also used. These typically they use quartz halogen bulbs. Fog lights are available in different shapes and sizes.Fog lights are usually mounted lower then headlights and tend to be aimed to strike the road a short distance in front of the vehicle. The light from the fog light is then reflected up into the fog. This reduces the light reflected into the drivers eyes, providing better visibility.Fog lights will normally be wired with a relay and circuit breaker. The method of connection of fog lights will depend on local regulations. They may be wired to work only with park lights and to turn off when headlights are used. The body control unit normally controls the function of the fog lights when fitted as original equipment. Cornering lights

SummaryCornering lights are white colored lights usually fitted into the bumper bar and are designed to provide side light when the vehicle is turning corners.

To improve visibility during night driving, some vehicle manufacturers provide cornering lights.Cornering lights are white colored lights usually fitted into the bumper bar and are designed to provide side light when the vehicle is turning corners.The additional lighting provided by cornering lights helps the driver to see the curb and any obstacles that may not be illuminated by the headlights.Cornering lights turn on only when the headlights and turn signal switches are on, so they only come on when the vehicle is turning the corner, and turn off automatically when the turn signal turns off. Smart lighting

SummaryDifferent lighting technologies can be fitted individually or together to form comprehensive adaptive lighting systems.

Different lighting technologies can be fitted individually or together to form comprehensive adaptive lighting systems.Automatic headlight leveling systems ensure that the headlights are always correctly aligned regardless of the load the vehicle is carrying. When a vehicle is loaded, the suspension settles causing the angle of the headlights to the road to change. This can cause glare into oncoming traffic. Auto leveling headlights use a sensor to monitor the angle of the vehicle to the road. This information is then used to automatically adjust the headlights. They adjust up or down so the headlights always stay correctly adjusted. In this system, the load sensors provide information to a control module that operates servomotors fitted to the headlights causing the headlights to tilt up and down.Some types of headlights can improve forward lighting while cornering. This type of headlight swivels through the horizontal plane so that the headlight turns into the corner as the driver turns the steering wheel. This provides better illumination of the road and verge as the vehicle turns through the corner. In this system sensors from the steering wheel provide information to a control module that operates servo motors fitted to the headlights, causing them to swivel.Headlight systems have traditionally used reflector type lighting systems. In a reflector headlight, the light from the bulb is reflected forward by a specially shaped reflector. An alternative is a projection type headlight system. This type of headlight often has a smaller front lens, however it produces a high intensity forward beam. It uses a lens system to project the light forward rather than the traditional reflector system. Park & tail light circuits

SummaryRed tail lamps and white park lamps are low wattage lamps that allow the vehicle to be seen by other road users. They are connected in parallel.

For motor vehicles and trailers, two red tail lamps operate when the headlight switch is in the park position and the headlight position. The two lights are located close to the widest points of the vehicle so that the vehicle width can be seen by other road users.The bulbs are connected in parallel to each other so that the failure of one filament will not cause total circuit failure. A number plate illumination lamp is usually connected in parallel to the tail lights and operates whenever the tail lights are on.Tail lights are usually incorporated in a cluster assembly at the rear of the vehicle. Government regulations control the height of the lamps and their brightness.The park lights, sometimes called clearance lamps, are located at the front of the vehicle and are used at night time when the vehicle is parked on the side of the road. They use low wattage bulbs and may have a lens or diffuser that makes the emitted light wide spread. In some cases, the park lights are incorporated in the headlight assembly.The park lights operate when the light switch is moved to the first position. For safety reasons the park and tail lights continue to operate when the light switch is moved to the headlight position. The bulbs are connected in parallel with each other.The circuit for the park and tail lights includes: the battery, fusible links and fuses, park light switch the lights at each corner of the vehicle the number plate light, the wiring to connect the components together, and the ground circuit to complete the circuit to the battery through the vehicle frame.When the park light switch is closed current flows from the battery, through the fusible link to the park light switch, where it is fed through the fuse to the front park lights and to the rear tail and number plate lights.After passing through the filaments the current path is completed through the frame of the vehicle to the negative battery terminal. Headlight & dip circuits

SummaryDip or low beam is used in built-up areas or when the driver of an approaching vehicle could be dazzled by the main beam.

Bright, well adjusted head lights are necessary for safe vehicle operation at night. The main beam provides a bright light suitable for driving on open country roads.The dip beam only is used in built up areas. In country areas, the dip beam is used whenever oncoming traffic could be dazzled by the main beam.The headlight circuit consists of: the battery, fusible link and fuses, head light switch, headlight relays, dipper switch, head lights, high beam indicator light, wiring of a suitable size to carry the electric current through the circuit and the ground circuit.When the headlights are switched on, current is supplied from the battery, through the fusible link and fuse, across the closed switch contacts to the dipper switch.In the dip beam position, electrical current can flow from the dipper switch contacts through the low beam relay winding to ground.This creates a magnetic field that closes a set of contacts. Closing the contacts allows electrical current to flow from the battery, through the fusible link, to the relay contact. From the closed relay contacts the current flows to the light filaments and then to ground.The park and tail lights are also in operation when the headlights are switched on. Lighting system

SummaryThe lighting system allows the driver to see when driving at night or in poor visibility conditions, and to signal to other drivers.

Lighting systems improve visibility at night, and make a vehicle visible to other road-users.A lighting switch operates tail-lights, park lights, and headlights to allow the driver to see ahead. A dip switch allows the driver to change the beams from high to low, or vice-versa, as required.Stop-lights operate when the brake pedal is depressed.Turn-signals alert other drivers of a change in direction, and are mounted so they can be seen from the front, rear and sides of the automobile.An emergency flasher system operates both front and rear turn-signals at the same time.Other circuits operate courtesy, or convenience lights, reversing lights, and fault indicators. Circuit diagrams

SummaryCircuit diagrams contain information about wire size, wire color, earth locations and shape and location of electrical connectors around the vehicle.The layout of electrical circuits and their components are shown as diagrams made up of symbols and connecting lines. Being able to read a circuit diagram is important when trying to trace and correct a fault in an electrical system.Not all circuit diagrams use the same symbols or the same numbering system so refer to the manufacturer's service manual for specific details on how to read a particular circuit diagram.This is a typical example of how a circuit diagram for a vehicle lighting system might be constructed.1.This is the park and tail light circuit.2.To this circuit we add the circuit for the headlights and dipped lights.

3.Now we include the stop light circuit.4.Then we add the reversing light circuit.

5.And the indicator or turn signal circuits.6.The completed circuit diagram represents all the wiring for the external lighting of a motor vehicle. Other circuits such as ignition, charging & starting circuits can be constructed in a similar way and added to provide a complete vehicle wiring system.

Networking & multiplexing

SummaryA multiplex network reduces the number of wires in the wiring harness and greater vehicle content flexibility.

Even the most basic vehicles include many electronically controlled systems. If each electronic system had its own ECU, harness and sensors, the weight of the added components would negate any efficiency it provided. A vehicles' multiple electronic systems could require over 1 mile or 1.6 Kilometers of insulated wiring, consisting of around 1000 individual wires and many terminals.One solution to the problem is the use of a system that integrates sensors into a common wiring harness by combining all the individual systems, where possible, into a multiplexed serial communications network, so they can share the information.An added advantage of such a system is that if there is less wire and fewer connections there is less chance of dirty connections causing faults.This system is referred to as a Controlled Area Network BUS or CAN BUS and it uses two thin wires to connect, or multiplex, all the control units and their sensors to each other. The output devices are referred to as Nodes.The advantage of a multiplex network is that it enables a decreased number of dedicated wires for each function, and therefore a reduction in the number of wires in the wiring harness, reduced system cost and weight, improved reliability, serviceability, and installation.In addition, common sensor data, such as vehicle speed, engine temperature, etc. are available on the network, so data can be shared, thus reducing the number of sensors.Also, networking allows greater vehicle content flexibility because functions can be added or modified through software changes.Other control units can be added to the system by simply connecting them to the network.A diagnostic tool can be connected to the CANBUS to extract operational information to assist in diagnosis and fault finding. Checking lighting & peripheral systems

SummaryThe objective of this procedure is to show you how to check peripheral lighting systems. Be sure to work in a systematic manner or you could miss a faulty bulb or another component.Part 1. Preparation and safetyObjective Check peripheral lighting systems.

Personal safetyWhenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include: Work clothing - such as coveralls and steel-capped footwear Eye protection - such as safety glasses and face masks Ear protection - such as earmuffs and earplugs Hand protection - such as rubber gloves and barrier cream Respiratory equipment - such as face masks and valved respiratorsIf you are not certain what is appropriate or required, ask your supervisor.Safety check Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.Points to note Be sure to work in a systematic manner or you could miss a faulty bulb or another component. A vehicle may have warning lights that will activate only if that circuit is in use. You may need to turn that circuit on to see the warning light. If you are unsure of where these are, ask your supervisor.

Part 2: Step-by-step instruction1. Check instrumentationIn a darkened area, turn on the ignition. The dash warning lights should be displayed. Start the engine. If any warning light stays on when the engine is started, it could indicate a problem in one of the cars safety or mechanical systems. If you are unsure about what any of the warning lights mean, consult the manufacturers manual.2. Check the car hornMake sure the car horn is working. If the horn is not working, locate it under the hood with the help of the manufacturers manual. Check the wiring to make sure there is a good contact. If necessary, use a DVOM to isolate the fault.3. Check rear lightsHave someone stand behind the vehicle to report any problems, then turn the ignition on. Switch on the park lights and tail lights. Do the same for left and right turn indicator lights. Depress the brake pedal to make sure the brake lights work.4. Check front lightsWith somebody in front of the vehicle, make sure the high and low headlight beams, the park lights, and the turn indicators are all working properly.5. Check interior lightsWith the interior light switch in the correct position, open the drivers side door to make sure the interior lights work. If any of these lights do not operate, you may need to replace a bulb, or a fuse. Check the fuse first, using a DVOM to check continuity. If the fuse is at fault you should report this to your supervisor, as there could be a more serious fault in the vehicles wiring system. Checking & changing an exterior light bulb

SummaryThe objective of this procedure is to show you how to check and change an exterior light bulb. Before replacing the bulb, check the bulb holder for corrosion. Clean any corrosion with abrasive tape.Part 1. Preparation and safetyObjective Check and change an exterior light bulb.Personal safetyWhenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include: Work clothing - such as coveralls and steel-capped footwear Eye protection - such as safety glasses and face masks Ear protection - such as earmuffs and earplugs Hand protection - such as rubber gloves and barrier cream Respiratory equipment - such as face masks and valved respiratorsIf you are not certain what is appropriate or required, ask your supervisor.Safety check Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.Points to note Make sure that the fuses are in good condition before attempting to change a bulb in a circuit that has more than one bulb, such as the turn signal circuit. If none of the bulbs are working, there may be a bigger problem to resolve.

Many light bulbs have more than one filament inside them. These bulbs normally have offset pins to ensure proper locking in the socket. Be sure to look carefully at the bulb you are replacing to make sure you do not try to force the bulb in the wrong way. Some bulbs have a colored glass envelope that enables them to be used with a clear lens. If you replace a bulb of this type, make sure that you replace it with one of the same color.

Part 2: Step-by-step instruction1. Access the bulbDetermine the method used to secure the lamp unit or lens cover and remove the cover to expose the bulb. If no screws are found on the lens cover, it may be necessary to remove the entire assembly to access the bulb.2. Remove the bulbIf the bulb is pin-mounted, gently grip the bulb and push it inwards. Turn the bulb in a counter-clockwise direction and remove it from the bulb holder.3. Check bulb holder for corrosionInspect the bulb holder to make sure there is no corrosion. If there is, clean it with abrasive tape.4. Insert the new bulbInsert the new bulb into the bulb holder, depress it fully, turn it clockwise and release it. Make sure the bulb is secure, and test its operation by switching it on and off.5. Replace cover and testReplace the cover, and test it again. Checking & changing a headlight bulb

SummaryThe objective of this procedure is to show you how to check and change a headlight bulb. Always make sure that you replace a bulb with one of exactly the same type. Otherwise, change both lights at once, so they always show the same intensity in lumens.Part 1. Preparation and safetyObjective Check and change a headlight bulb.Personal safetyWhenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include: Work clothing - such as coveralls and steel-capped footwear Eye protection - such as safety glasses and face masks Ear protection - such as earmuffs and earplugs Hand protection - such as rubber gloves and barrier cream Respiratory equipment - such as face masks and valved respiratorsIf you are not certain what is appropriate or required, ask your supervisor.Safety check Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.Points to note There are many types of headlight bulbs available. Always make sure that you replace a bulb with one of exactly the same type. Otherwise, change both lights at once, so they always show the same intensity in lumens. Sealed beam units require that the whole unit be replaced when one filament has failed. If the reflector in the lamp unit shows signs of internal blistering, that also indicates that you must change the unit.

If both lights operate but are not bright when switched on, start the engine to see if this solves the problem. The battery may be in a poor state of charge. Another explanation is that the system may have a bad ground connection. This would have to be checked with a DVOM. Touching a new halogen bulb with your fingers can leave some greasy residue from your fingers on the outer surface. This can cause the bulb to burn out very quickly. If you inadvertently touch the bulb, clean it with an alcohol-based substance. Do not use gasoline or paraffin to clean the bulb.

Part 2: Step-by-step instruction1. Check headlight operationAssessing headlight operation is always best carried out in a low light environment. Switch the vehicle headlights on to low beam, then switch to high beam. Check that the main beam indicator on the instrument panel is operating. Note the change in the intensity of the lights. If one of the lights does not operate that headlight will need replacement.2. Identify headlight typeDetermine the type of lamp fitted to the vehicle, and obtain a replacement. Many vehicles today are equipped with halogen type headlights. These are twice as powerful as older sealed-beam units and need to be handled carefully. Always follow the manufacturers handling instructions.3. Access the lamp socketUnplug the electrical connector at the back of the lamp unit. On most vehicles it is not necessary to remove the lamp unit from the vehicle. Unscrew the bulb-retaining ring.4. Remove and replace the old bulbRemove the old bulb and replace it with the new one. Handle the new bulb only by its base or, if supplied, by the card cover. It is very important that you never touch the surface of the bulb with your fingers, as this will cause it to burn out very quickly.5. Replace the headlight unit and testReplace the unit and the retaining ring or bulb assembly, and then re-plug the connector. Switch on the lights again to confirm that they are both operating correctly. Aiming headlights

SummaryThe objective of this procedure is to show you how to use a headlamp adjuster unit to aim headlights. Although the principle of aiming headlights is the same in the majority of cases, the legal rules can differ from region to region. Be sure to check the requirements for your location.Part 1. Preparation and safetyObjective Use a headlamp adjuster unit to aim headlights.Personal safetyWhenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include: Work clothing - such as coveralls and steel-capped footwear Eye protection - such as safety glasses and face masks Ear protection - such as earmuffs and earplugs Hand protection - such as rubber gloves and barrier cream Respiratory equipment - such as face masks and valved respiratorsIf you are not certain what is appropriate or required, ask your supervisor.Safety check Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.Points to note Although the principle of aiming headlights is the same in the majority of cases, the legal rules can differ from region to region. Be sure to check the requirements for your location. If you are unsure of what these are, ask your supervisor.

Some manufacturers may suggest that the headlights be aimed on high beam, others on low or dipped beam, depending on the number of lights and type of application. They may also suggest that a load be placed in the vehicle. Refer to the manufacturer's manual for specific information regarding headlight aiming.

Part 2: Step-by-step instruction1. Check tire pressuresMake sure the car is on an even and level surface and that the tires are inflated properly. Over loading the rear of the vehicle can alter the alignment, so make sure the check is done according to the manufacturers loading recommendations.2. Position vehicleMove the vehicle into the correct position in relation to the headlamp aligner unit following the equipment manufacturer instructions.3. Check low beam settingsTurn the headlights on to a low beam setting. The center of the illuminating beams should be in the lower right quadrants of the chart or wall markings.4. Check high beam settingsThe high beam should be centered, falling on the intersections of the horizontal and vertical marks.5. Adjust headlight alignmentIf necessary, locate the adjustment screws on the headlight and turn them so the lights point to the correct places.6. 7. 8. 9. 10. 11. 12. Security systems13. 14. 15. 16. Summary17. Theft deterrent systems can be divided into four different categories: component identification; vehicle locking; engine and transmission immobilization; and audible alarms.18. 19. In an effort to reduce theft, some vehicle manufacturers fit very sophisticated theft deterrent systems to their vehicles.20. Theft deterrent systems can be divided into four different categories. Component identification; vehicle locking; engine and transmission immobilization; and audible alarms.21. Visible identification of major components can be a deterrent for theft. Some manufacturers have etched the Vehicle Identification or VIN Number onto labels that are attached to various components on the vehicle such as fenders, doors, the hood and trunk as well as major mechanical components such as the engine and transmission.22. Etching the Vehicle Identification Number onto all windows with a small sand blaster is unobtrusive and makes the vehicle less attractive to steal. If the vehicle is resold or used for parts the monetary value is reduced.23. Microdots are small plastic particles that can have either the VIN or a unique number printed on to them. They are almost invisible to the naked eye, but can be seen by using an ultra-violet light and a magnifying glass. They are mixed with an adhesive and sprayed onto the underside of the vehicle, into the wheel wells and engine bay. A small transfer affixed to the vehicle displays that this system has been used, making the vehicle less attractive to a thief.24. Door lock systems can be manual entry, where a key has to be inserted into the door lock and turned; or keyless, where a button on the key or key fob is pressed; or the door unlocks automatically as a driver carrying the correct security device approaches the vehicle.25. On older vehicles, turning the key in the door lock would unlock only that door. The remaining doors needed to be unlocked manually, via the lock snib or lever. Releasing the key would return it to the same position it was in when inserted so it could be removed.26. When central locking was introduced, the lock mechanism on the drivers door had a micro switch that, when turned, would activate electric solenoids on the remaining doors and trunk and unlock them. The same applies when the doors were locked.27. Further enhancement allowed manufacturers to introduce a security system that automatically locked the doors once the vehicle had reached a preset speed. This feature is mandatory in some countries.28. Dead locking adds a further level of security, so that if the key were turned a quarter turn and removed a second micro switch activates small electric motors in each door lock mechanism, mechanically locking them.29. 30. 31. 32. 33. 34. 35. Remote control keys36. 37. 38. 39. Summary40. Remote control keys and key fobs transmit a coded signal that is received by the vehicles theft deterrent module.41. 42. Remote control keys and key fobs transmit a coded signal that is received by the vehicles theft deterrent module. If the code meets preset criteria, the module closes a switch that enables either the drivers door or all doors to be locked and unlocked as required.43. Pressing the button a second time when locking some vehicle activates the dead lock actuators and deadlocks the vehicle.44. For the remote key and computer to exchange information, wireless communication is needed. High frequency electromagnetic fields known as Radio Frequency or RF is used. This system relies upon the same basic technology as cell phones, TV and radio.45. The remote fob can have one button to lock and unlock; 2 buttons, one to lock and the other to unlock; 3 buttons, where the third button activates the trunk or tailgate; or 4 buttons, where the fourth activates a panic alarm, locking the doors, sounding the horn and flashing the headlights and hazard lights.46. Some vehicles actively transmit a radio code looking for a specific key. As the driver approaches the vehicle, the vehicle locates the key and the theft deterrent module unlocks the vehicle. When the driver leaves the vehicle and the key is out of range the theft deterrent module locks the vehicle.47. When keyless entry is used, personalization of systems is possible. They can be programmed to recognize different keys, with each driver having their own specific key. This allows for different settings to be made that are individual to each driver.48. When a specific key is identified, the theft deterrent module communicates with the body control unit. Specific settings are remembered from that key, so the seat, steering wheel and mirror position automatically adjusts to the driver as well as climate control settings for cabin temperature and system modes. Entertainment system settings such as radio station presets, volume and audio settings; and transmission shift point preferences can all change to the drivers individual preferences.49. It also allows for a valet key to be used, limiting engine power and vehicle speed, and preventing any other vehicle settings from being changed.50. Immobilization is where the theft deterrent system prevents the vehicles engine starting, or the transmission operating. Audible alarms may sound when either the locking or immobilization systems are tampered with.51. 52. 53. 54. 55. 56. 57. Theft deterrent systems58. 59. 60. 61. Summary62. Theft deterrent systems aim to prevent the vehicle being entered, started or driven by reacting to input from devices such as door locks and vibration sensors, and by controlling such things as the starter motor or engine to immobilize the vehicle.63. 64. Theft deterrent systems aim to prevent the vehicle being entered, started or driven. The actuators used to achieve this are the electric door locks and windows, the starter motor relay, engine management systems, transmission shift solenoids, and an audible alarm.65. The computer that controls the system monitors input signals from various devices. Switches are located at each door, the hood and trunk openings, and the fuel filler door.66. Vibration sensors detect any unusual vehicle movement such as lifting, jacking or towing.67. Ultrasonic sensors detect any movement inside the cabin.68. Voltage monitoring sensors check against operation of the starter motor, ignition system or fuel pump.69. The immobilization system is enabled by pressing the lock button on the remote key, locking the doors manually with the door key, or when a period of time has elapsed, typically 15 seconds, after the engine has stopped. The immobilization system is disabled by pressing the unlock button on the remote fob.70. The key fob and theft deterrent computers have to be capable of transmitting and receiving coded information. Operational characteristics vary greatly between manufacturers, and because it is a theft deterrent system, details are a close kept secret.71. Most systems use a coded system known as rolling codes. The coded data transmitted and received between the key fob and theft deterrent computer randomly changes. This creates a situation where the code used to lock and immobilize a vehicle is different to the one used to unlock and mobilize a vehicle. Manufacturers who use this system have seen a dramatic reduction in theft, noticeably from joy riders. The code is transmitted as a digital number, typically containing 16 digits, giving the possibility of billions of different code numbers. When the lock button is pressed, the control unit and key preset the agreed code, which will be used to unlock the vehicle and deactivate the theft deterrent.72. Pressing any button on the remote fob transmits an RF signal, even if the vehicle cannot read it, and changes the rolling code unit from that exchanged between the control module and the fob. The system allows an error factor of 25 steps either side of the agreed code for deactivation before the fob transmits a False Code, where the control module will disregard the key.73. 74. 75. 76. 77. 78. 79. Integrated communications80. 81. 82. 83. Summary84. Modern vehicles integrate audio, video and communication systems into a network.85. 86. Modern vehicles integrate audio, video and communication systems into a network. This allows for a high quality, compact and ergonomic system, which combines entertainment features with simple operation.87. Controls are centralized with hardware, such as CD stackers, and DVD players located remotely.88. Communication between components uses a combination of hard wiring and data buses.89. With data buses being used, audio messages can be broadcast over the audio system that relate to other vehicle systems. For example, a voice message can say the park brake is on or left rear tire is under inflated90. The system allows for features such as the interruption or replacement of audio entertainment when there is an incoming phone call, or simply muting the audio to allow a hands-free phone conversation.91. Audio control functions are usually located on the central control pod or on the components head unit. Vehicles can integrate the common audio controls on the steering wheel to allow for safer driving.92. The music played on a system usually comes from one of several sources. Magnetically on a cassette tape, optically on a CD or DVD, by radio frequency from radio stations or satellites, or from other portable devices.93. The information is decoded or processed by the control unit and outputted to drive speakers located throughout the vehicle.94. Another function provided by the body control unit is that of speed dependant volume. The control unit has an input from the vehicle speed sensor, which allows it to gradually increase audio system volume proportionally with road speed. As speed, and therefore engine and road noise increases, the audio volume will increase. As speed decreases the audio volume will decrease.95. Viewing screens for onboard TV, DVD and games can be located in the dash, however, if the screen is viewable by the driver it must disable when the vehicle is in motion. Other mounting points are from the roof or integrated into the rear of seat headrests.96. Control units can be hard wired, or wireless using an infrared remote control.97. 98. 99. 100. 101. 102. 103. Body controlled lighting systems104. 105. 106. 107. Summary108. In modern vehicles ambient light sensors are used to automatically turn the headlights on in low light situations. Other body control lighting features can include: automatic 'dipping' headlights; delayed 'off' headlights; and headlight warning alarms109. 110. When driving at dusk the ambient light can fade slowly. In some vehicles an ambient light sensor determines when light levels are low. This is read by the body control unit, which turns the headlights on.111. Automatic dipping headlights use a sensor located at the front of the vehicle to detect light from oncoming vehicles. If the headlights are on, low beam is selected automatically. This prevents oncoming traffic being dazzled by the vehicles high beam.112. Delayed off allows the headlights to be left on after the engine has stopped and the doors locked. The headlights will automatically extinguish after a period of time, allowing the driver to safely see their way from the vehicle.113. On some vehicles the body control unit will turn the headlights off if the headlights are left on after the ignition switch is turned off and the drivers door is opened.114. On other vehicles headlight warning alarms sound if the headlights are left on after the engine has been turned off and a door is opened. This reduces the risk of the headlights draining the battery.115. The body control unit illuminates a warning light when an exterior lighting bulb or globe such as a stop, tail or flasher light has failed. To do this, the body control unit compares current flowing through these circuits to values stored in the computers memory. If the current flowing is outside set parameters the warning light is illuminated116. The body control unit can be programmed to keep the interior light illuminated after the doors have been closed for a set period of time, to allow the occupants to locate seat belts or insert the ignition key. It will also illuminate the light when the ignition is turned off to allow the occupants to locate door handles and luggage items.117. 118. 119. 120. 121. 122. 123. Proximity sensors124. 125. 126. 127. Summary128. Proximity sensors are mounted in the front or rear bumpers. The control unit determines the distance between the sensor and an obstacle by measuring the time taken for sound waves to leave and return to the sensor.129. 130. To allow for safer parking, proximity sensors can be mounted in the front or rear bumpers.131. These color-matched sensors emit ultrasonic sound waves that the human ear cannot detect.132. These piezo sensors are used to transmit and receive coded sound waves. The control unit determines the distance between the sensor and an obstacle by measuring the time taken for the sound wave to leave and return to the sensor. Normally 4 sensors are used to allow for full coverage across the width of the vehicle.133. Proximity to obstacles can be indicated by separate audible and visual alarms, or by integrating warning sounds with the vehicles audio system.134. If a trailer is attached to a coupling, the rear sensors are disabled automatically when the harness plug is inserted. Front sensors can be disabled manually in stop start or stop and go traffic.135. 136. 137. 138. 139. 140. 141. Reflective displays142. 143. 144. 145. Summary146. Reflective displays use a mirror embedded in the dash so the instruments appear further away than they actually are. This way the driver's focal point changes less when looking from the road to the instruments and back.147. 148. Conventional instrument panels require the driver to change the line of sight and their visual focal length to read information on the instrument cluster. This means the driver is looking away from the road for a significant distance when traveling at speed.149. Reflective displays are mounted within the dash panel. They use a mirror embedded in the dash, forward of the driver, to reflect an image of the instrument cluster. The actual instruments are hidden in the dash and it is a reflected view of them that the driver sees.150. This has the effect of the instruments appearing to be located further away than they actually are. The benefit of this system is that the drivers focal point changes less when looking from the road to the instruments and back.151. 152. 153. 154. 155. 156. 157. Global positioning satellites (GPS)158. 159. 160. 161. Summary162. A system known as a Global Positioning System, or GPS, can be used to determine the exact location of a vehicle on the earth's surface.163. 164. Thousands of satellites, serving a variety of purposes, are continually in orbit high above the earth. The use of satellite technology in vehicle systems provides an ever-increasing array of options for vehicle manufacturers. It is an area of automotive technology that increases the flexibility and power of many onboard systems.165. Satellite technology is used in: Navigation, vehicle tracking, vehicle theft recovery, communication, and internet access.166. A system known as Global Positioning System, or GPS, can be used to determine the exact location of a vehicle on the earths surface. The GPS forms a critical part of vehicle tracking systems, however many other components are required to keep track of the vehicle.167. Mountains, tunnels, large buildings and other objects can interfere with satellite communication and make it unreliable.168. Most vehicle tracking systems can work very accurately without satellites once their initial position has been determined. On board sensors can be used to keep track of the exact vehicle location.169. 170. 171. 172. 173. 174. 175. Triangulation/trilateration176. 177. 178. 179. Summary180. Trilateration or triangulation is the system whereby a vehicle's location is determined by forming a triangle with a group of four or more satellites.181. 182. The Global Positioning System or GPS uses a group of at least 24 satellites orbiting approximately 12 600 miles or 20 200 kilometers above the earth. The vehicle is equipped with a receiving antenna and computer system. The GPS receiver on the vehicle has to locate four or more of these satellites, determine the distance to each, and use this information to establish it's own location. This operation is based on a mathematical principle called trilateration.183. Trilateration in three-dimensional space is quite complex. For ease of understanding, the term that is generally used in the automotive industry to describe how the GPS positioning system operates, is Triangulation.184. Triangulation is the process of finding the position of an unknown point based on forming a triangle with two known points.185. For simplicity, the dimensions used to determine these points are commonly known as Latitude, Longitude and Elevation186. If a group of three satellites are taken to form a triangle, 12 600 miles or 20 200 kilometers above the earth, the shape and size of this triangle will never change.187. Equally any fixed point on the surface of the Earth will triangulate with the satellites. The numbers of fixed points are infinite.188. What the GPS does to work, is form many triangles with different pairs of satellites.189. Each satellite has an atomic clock onboard and regularly transmits a unique radio frequency signal simultaneously with all other Global Positioning Satellites. The RF signals travel out across space in all directions.190. The speed at which an RF signal travels in space is approximately 186,000 miles or 300,000 kilometers per second, the speed of light in a vacuum.191. Each of these transmitted signals will reach the GPS antenna of the vehicle. The time taken for the RF signal to travel from each satellite and arrive at the vehicle is dependant on the distance each satellite is from the vehicle. The greater the distance the longer the time taken.192. The vehicles onboard GPS system needs to know three things to determine the location of the vehicle.193. The time it takes for the signal to travel from the satellites to the vehicle.194. The location of each satellite195. And accurate time.196. Given these facts, enough information is available to form a three dimensional figure of a pyramid with a triangle base.197. The base of the pyramid is formed by the location of the satellites and the apex of the pyramid is the location of the vehicle on the Earth, a point derived from triangulation of the known points of the base.198. The GPS equipment knows that all of the apexes (the position of the GPS) of each triangle must be in the same literal position.199. Adding more satellites makes this more accurate because it gives the GPS more triangles to work with.200. Satellites are positioned so that every location of the earths surface has access to four satellites 24hrs a day.201. Satellites rely on the use of solar energy for their operating power and to maintain position. As the earth and moon move through their orbits, varying gravitational forces are placed on the satellites. The system allows for accurate positioning ensuring the satellites do not move from their correct location.202. Inaccuracies caused by weather conditions do occur as the RF signal moves into the earths atmosphere it travels through air, with varying levels of density. This slows the speed at which the RF signals travel.203. Inaccuracies also occur when RF signals are reflected off objects such as large buildings. Solar radiation can also cause inaccuracies.204. 205. 206. 207. 208. 209. 210. Satellite navigation211. 212. 213. 214. Summary215. Once a vehicles position is determined via trilateration, software can be used to generate an accurate map of the area. The GPS continues to provide updated information to ensure accuracy of the map data.216.

217. Trilateration is used to determine an initial vehicle position for reference. Once this has been determined, mapping software stored on a DVD can be used to generate an overlay map and data for the driver on a display screen. As the vehicle moves the GPS continues to provide the necessary information to allow for plotting of position on the map.218. Various DVDs are available to cover the different continents.219. Accurate and reliable navigation is still possible even when satellite signals become unavailable. This is achieved by using electronic sensors to monitor vehicle variables such as: Pitch, roll, yaw, road speed, steering angle, acceleration, and deceleration.220. By using the information from these sensors, the navigation system is not continually and totally reliant on satellites.221. During normal operation, the computer program compares vehicle position data derived from the satellites, and onboard sensor information, to ensure high levels of accuracy. In addition, ground based stations may be used in suitable locations, as an absolute reference point.222. Satellite navigation features can include: Multiple languages and a choice of voice gender and destination and journey plotting, where the most suitable route is provided and deviation from the recommended route causes the system to provide an alternate route.223. It can also include directional information provided with a combination of screen icons, maps and audible instructions; a self-learning route memory function; congestion avoidance, which can warn of the latest traffic bottlenecks and suggest alternative routes; various monitor color display settings; infra red remote control; trip computer; speed dependent setting; and telephone mute for sound systems.224. 225. 226. 227. 228. 229. 230. Telematics231. 232. 233. 234. Summary235. Automotive telematics is a satellite-based system that combines two-way communication and information technology within the vehicle.236.

237. Automotive telematics is a satellite-based system that combines two-way communication and information technology within the vehicle. The vehicle is equipped with a satellite transceiver enabling data to be sent to and from the vehicle.238. Using this system allows for: vehicle tracking, monitoring of onboard systems, messaging, travel information, entertainment, security, safety and fleet management systems which monitor information such as location, distance traveled, speed, stops and fuel usage.239. A vehicle manufacturer may offer telematics as a service to its customers. The benefits of this can include: the location & immobilization of a stolen or lost vehicle, notification to emergency services after SRS deployment, engine shut down and door unlocking in the event of a severe accident, roadside assistance and remote diagnosis. Airbags

SummaryThere are a number of different types of air bag, including: driver & passenger frontal impact air bags, side impact air bags, and curtain side air bags. There are two different types of air bag triggering mechanisms - electrical and mechanical

Airbags are usually described as a Supplemental Restraint System, or SRS, but in some countries, wearing seat belts is not mandatory in which case air bags then become the primary restraint mechanism, and they would need to trigger at lower speeds and be larger in volume. There are a number of different types of air bag, their size and location determined by the type of protection they offer.The most common location for an airbag is in the center of the steering wheel. It protects the driver from frontal impacts. Airbags are also commonly fitted to the passenger side of dashes for the same reason. Side impact air bags are located in the sides of front seats to protect the occupants from side impacts. Curtain side air bags are located in the side edge of roof linings to protect the occupant s head from side impacts.The air bag assembly consists of: a nylon bag squib igniter gas generator and an air bag triggering mechanism.There are two different types of air bag triggering mechanisms - electrical and mechanical. Most air bags are triggered electrically, with a small electric current delivered from a remote SRS control unit. Mechanically activated systems use inertia to move a triggering pin. Regardless of the type the triggering mechanism, the air bag deploys due to simultaneous explosions occurring within the squib, the igniter, and the gas generator. All three of these are located in a metal housing attached to the back of the air bag assembly.When the control unit determines the air bag should be deployed the electric current triggers the squib. The heat generated causes the igniter to burn, which in turn explodes the gas generator. The high-pressure nitrogen gas is produced and the air bag rapidly inflates. When the air bag assembly is mounted, it sits behind a pad which has a fracture line cast into the inner face. When the air bag deploys, the force of the generated gas causes the line to rupture, allowing the bag to fully inflate.Mechanically deployed air bags do not have any electrical circuitry. The squib is ignited with a firing pin. Under severe deceleration, inertia causes a steel ball to release a firing pin into the squib. Once the squib has been triggered, the deployment process is identical to electrically triggered air bags. The air bag is fully inflated within three hundredths or 0.03 of a second, cushioning the head and upper chest of the occupant as it moves forward.The air bag is made from nylon and is folded into the front face of the assembly. It is coated in cornflower, which acts as a lubricant during deployment. Holes are usually located in the rear face of the air bag to allow the nitrogen gas to escape. This deflates the air bag and provides a cushioned, rather than a hard surface, to help protect the occupant. Seatbelt

SummaryA seatbelt is a safety harness designed to hold the driver and passengers of automobiles firmly in their seats during an accidental collision.

A seat belt, or safety belt, holds a car driver or passenger firmly in their seat when a collision occurs. This reduces personal injuries by preventing occupants from being thrown about inside the vehicle and crashing into the dashboard or windshield or, in the case of rear passengers, from impact with the rear of the front seats.The most common type of seatbelt fitted to most vehicles is a three-point harness consisting of a lap belt from one side of the seat to the other, plus a second belt going from the inner lap anchor point up and across the wearer's torso to an anchor point on the inside shell of the vehicle behind and above the wearer's shoulder.A five-point harness is more common in child safety seats. This has a lap belt, two shoulder belts, and an extra belt going up from the center front of the seat vertically between the wearer's legs. Five-point harnesses are also common in racing cars.The lap belt is usually on a free-running retracting mechanism, so that any slack is always taken up and the belt fits snugly against the occupant but without restricting general movement during normal driving. When the belt is pulled hard, or if the vehicle is under brakes or cornering, or during a collision, the roller mechanism locks, holding the occupant firmly in the seat during an impact. Some seatbelt mechanisms have a pretensioner built in which actively tightens the seatbelt more firmly when an impact occurs.It is generally accepted that wearing seatbelts reduces the probability of death or injury in a collision. For that reason, wearing seatbelts at all times when inside an automobile is now mandatory in many countries. Vehicle safety systems

SummaryVehicle safety systems are designed to protect occupants during accidents. They include primary systems, such as bumper bars & seat belts; and secondary systems, such as air bags.

Vehicle safety systems are designed to protect occupants during accidents, and can be classified as primary, or passive systems and secondary, or active systems.Primary systems are ready to use in any accident. They include bumper bars, body panels, seatbelts, crumple zones and collapsible steering columns.A secondary system has to be activated to work and is only necessary in severe accidents. The two most popular types of secondary systems are supplemental restraint system air bags, and seatbelt pre-tensioners.Seatbelts locate and secure the occupant within the seat and vehicle cabin, and in minor collisions perform their task well.In a more severe impact inertia causes the occupant to move more and with greater force. This increases the possibility of injury caused by the restraining force exerted by the seatbelt or from the occupant striking interior fittings.If a vehicle is fitted with an air bag, it deploys during a collision, offering a greater degree of protection from injury.Air bags provide cushioning against the effects of inertia. The bag deploys towards the occupants approaching body, inflated rapidly by pressurized nitrogen gas. Typically this takes no longer than three hundredths, or 0.03 of a second.The air bag is not a nice soft pillow, but a strong counter force to react against the inertia of the occupants. It is not designed to be comfortable. It is designed to minimize injury.Immediately after absorbing the momentum, the air bag deflates having done its job. Crash sensors

SummarySensors are located behind the front bumper, headlights, dash and doorsill or 'B' pillar. Some manufacturers also place sensors within the electronic control unit.

Crash sensors can be fitted in various positions throughout the vehicle. Their location depends upon the direction of deceleration they are designed to detect.Some manufacturers place the sensors within the electronic control unit. Others are located behind the front bumper, headlights and dash.Side impact sensors are located in the doorsills or B Pillar. They will inform the SRS control unit of a side impact and whether to deploy the left or right side air bags.When the sensors indicate that a predetermined deceleration rate has been exceeded and it is from the appropriate direction, the SRS control unit deploys the relevant air bags.If the collision is from the front, the driver and passenger air bags will deploy.If the collision is from the side, the sensor determines whether the seat mounted air bag, or curtain air bags for one side of the vehicle will deploy.With more refined designs, the passenger air bag deploys only if there is an occupant in the seat. Deployment can also depend on the weight of the occupant and whether the passenger air bag switch, if fitted, is turned on.To prevent incorrect and unnecessary deployment, systems include a safing sensor mounted within the SRS control unit. The SRS control unit will only pass current through the squib if both the safing sensor and a crash sensor indicate simultaneously that a predetermined deceleration rate has been exceeded.The SRS warning light is illuminated, and stays on, if a fault is detected in the system.Capacitors within the SRS control unit are used to store electricity and act as a back up power supply. If a vehicle has its battery destroyed or disconnected in an accident, the capacitors supply the electricity required to keep the SRS system operational.Some seat mounted side impact air bags also operate without electricity. When the side of a vehicle is crushed inwards, a detonator mounted on the lower outside edge of the seat is detonated. Pyrotechnic tubes connect the detonator to the air bags, which in turn ignite the squib. Many vehicles use two stage side impact bags. This provides protection to the upper torso over a more extended time. Seat belt pre-tensioners

SummaryThere are two types of seat belt pre-tensioner, mechanical & electrical. Seat belt pre-tensioners are used to tighten the seat belt in a severe frontal accident.

Seatbelt pre-tensioners are used to tighten the seatbelt in a severe frontal accident. Both mechanical and electronic control systems are available. The most common type relies upon an explosive charge that is detonated electronically by a sensor within the seatbelt tensioning mechanism.This explosion moves a piston that pulls on a steel cable causing the belt to tighten by approximately 4 inches or 100 millimeters. The design allows for the belt to tension before the occupant has moved forward in the seat.Mechanical systems rely on inertia to move a sensing mass. This releases a spring to pull on a cable, thus tightening the belt.Once the pre-tensioner has triggered, a ratchet prevents the seatbelt from loosening. When the seat belt is removed from the buckle, it cannot be reinserted, and the assembly should be replaced.Rip stitching is used on seat belts in conjunction with an air bag and seat belt pre-tensioners. During a collision the pre-tensioners initially pull the seat belt tight, however the stitching gradually tears to allow the occupant to move forward into the air bag at a controlled rate.For safety reasons, these belts must be replaced once they have had their stitching ripped. Manufacturers generally fit warning labels within the fold to indicate the belt is to be replaced when the label is revealed. Tire pressure monitoring systems

SummaryAutomated Tire Pressure Monitoring Systems or TPMS provide a means of reliable and continuous monitoring of the vehicle tire pressure and are designed to increase safety, decrease fuel consumption and improve vehicle performance.

Maintaining proper tire pressure is essential for the safety and performance of a vehicle. It also plays a significant role in decreasing fuel consumption and extending tire life.All tires lose inflation over time and, as many modern vehicles have extended service intervals, tires can become dangerously under-inflated without regular checking by the vehicle driver.In addition to increased fuel consumption and tire wear, long periods of driving with low tire pressures can cause additional stress on the tire sidewalls. This results in increased operating temperatures that can lead to premature tire failure.Tires operating with low pressures can also affect the vehicle's handling and performance. In a worst-case scenario, under-inflation can lead to a tire blowout or tread separation.Automated Tire Pressure Monitoring Systems or TPMS provide a means of reliable and continuous monitoring of the vehicle tire pressure and are designed to increase safety, decrease fuel consumption and improve vehicle performance.There are two types of tire pressure monitoring; direct and indirect.The direct monitoring system uses a pressure sensor mounted inside each wheel and uses a wireless transmitter to give direct tire pressure readings.The indirect system uses the vehicles wheel speed sensors to determine if a tire is underinflated when compared to each of the other tires.TPMS can be fitted to all vehicle types using conventional and run-flat tires.With a Tire Pressure Monitoring System installed on a vehicle, drivers can monitor the tire pressures and temperatures from the driver's seat to ensure that their tires are properly inflated under all operating conditions. The systems are also designed to ignore normal pressure variations caused by changes in ambient temperature.The sensor installed inside each wheel is able to respond to as little as a 3PSI or 20Kpa drop in pressure. Real-time information is sent via wireless signal to a display in the vehicle. If a fluctuation occurs, an audible and visual warning instantly alerts the driver allowing time for the vehicle to be stopped or driven to a service station for tire repair or re-inflation. The tire is used to enclose the unit as protection from the outside environment. An on-board computer receives the radio messages from the sensors, which are coded for individual wheel identification.The interactive display inside the vehicle shows: The required tire pressure the actual tire pressure the tire pressure status and the temperature of the tireThe driver can use the display control buttons to check the status of each tire.In OEM installations, each time the ignition is switched on, an indicator on the instrument panel and on a system display provides information about all four tire pressures, and gives a "Pressure OK" message if all is well. An indicator on the display will flash whenever pressure loss is detected. In the case of minor deflation, an orange "Service" light is shown, and indicates the faulty tire. If the pressure is dangerously low, a red "Stop" light flashes, accompanied by a punctured tire icon, indicating that an immediate wheel change is needed.The sensors are activated by a centrifugal switch and transmit only when the vehicle is in motion. When the vehicle stops the sensors return to sleep mode to extend battery life, however the driver is still able to review the latest signals received from the wheels before the vehicle was stopped.


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