Supplementary Restraint System

Supplementary Restraint System

Switch on the ignition and make sure all warning lights operate. Check in

SRS warning Drivers airbag

particular the supplementary restraint position system (SRS) light, and that it goes out

light

when the engine starts. Inspect all air

bag positions for security. Side airbag

Passenger

airbag position position

ICE System Check the ICE system aerial for security. Test the ICE system by listening to each speaker in turn. Make sure you reset the unit to the customer’s preferences. A great looking set from Pioneer is shown here. The system has an Organic Electro-luminescent Display (OED).

Worksheet Service/Check seatbelt

Seatbelt lock

mechanism

operation. Caution: Some seatbelts incorporate tensioners

that operate in the event of a collision. Do not attempt to dismantle these systems without reference to the manufacturer’s data. Check for twisted webbing due to incorrect alignment. Adjust as required.

Seat Belts Fully extend each belt in turn and inspect the webbing. Look for cuts, damage, broken threads, colour fading and bowed webbing. If any

Checking the

damage is noted the belt should be renewed. Follow belt condition the manufacturer’s procedures for this process. If

the belt will not extend, check for contamination and twisting.

Safety Belt Operation Insert the tongue of each belt into its buckle. Pull hard to make sure it locks in place. Follow manufacturers’ procedures to renew Seatbelt

if in any doubt. Push the button to make sure the buckle

operation

belt releases from the buckle easily. Pull each belt in turn fully out and make sure it retracts. It is acceptable to guide the belt home and prevent twisting. However, the spring should pull the belt into its fully retracted position.

Friction and Inertia Belt Locks Pull sharply on each belt in turn to check that it locks up. Drive the vehicle in an area away from other traffic, and brake sharply from about 10 mph /16 kph. The driver’s belt should lock and hold you in position. Use an assistant to check the other belts if necessary.

Summary The previous tasks will normally be carried out as part of a general service. If extra work such as damage or incorrect operation is noticed, this should be reported to the customer.

 Look back over the previous section and write out a list of the key bullet points here:

BODY ELECTRICAL – CUSTOMER CARE Regular Checks Regular servicing is vital for a customer’s

safety. Carry out checks at all services and report your findings to the customer. Advise customers if anything will need attention before the next scheduled service interval.

Vehicle Condition Respect your customer’s vehicle and take precautions to keep it clean. Repairing or checking some systems, is likely to involve you working under the vehicle, and

then sitting in the driver’s seat. Use seat covers and ensure the steering wheel is clean when you have finished.

Keep Customers Informed Some customers like to know details of what work has been done to their vehicle – and they have Keep Customers Informed Some customers like to know details of what work has been done to their vehicle – and they have

Wiper motor

System Operation Some of the body electrical systems can appear complex, to the customer, at first view. However, they will appreciate you taking the time to explain the operation of these systems. For example, although the handbook contains instructions, showing your customer how the CD and radio remote control operates will be helpful.

Quality Replacement Components It is often tempting to increase the profit on a job by using ‘pattern’ parts. These are copies of the original components. Some of these components, produced by well-known companies (Bosch for example) are excellent quality and are used as original equipment by many manufacturers. However, some pattern parts are cheap, and you get what you pay for! One of the most irritating things for a customer is to have to return the vehicle for the same job to be repeated – and it wastes your time. Use good quality parts at all times.

Bosch wiper components

Safety Advice It is not possible to be specific about safety advice here as issues vary between manufacturers. Their instructions relating to safety should always be followed. One common issue however, is the positioning of a child or baby seat. Cars fitted with airbags, which is almost all modern vehicles, come with specific recommendations about where the seat should be fitted. Pass on this advice to your customer at all times.

Summary A customer, who is kept informed and treated with respect, will return and keep you in a job! Explain things to a

customer when asked – it will be appreciated.

MONITORING AND INSTRUMENTATION SENSORS

Introduction Sensors are used on vehicles for many purposes. For example, the coolant temperature thermistor is used to provide data to the engine management system as well as for the driver. The information to the driver is provided by a display or gauge.

Sensors The following screens list some of the things on a car that are sensed or measured, together with typical sensors. The sensors convert what is being measured into an electrical signal. This signal can

Sensors used for then be used to operate a

instrumentation display, such as a gauge or

warning light, on the instrument panel.

Fuel Level Fuel level is measured by using a variable resistor that is moved by a float. The position of

the float is determined by how …And empty

Tank sender

unit full…

much fuel is in the tank. The resistance value is varied by a contact sliding over a resistor.

Temperature The most common temperature measurement is that of the engine coolant. However, outside air, cabin, air intake and many other temperatures, are measured. A thermistor is used for most applications. A

Temperature sensor thermistor is a special material

that changes its resistance with temperature. Most types are described as negative temperature coefficient (NTC). This means that as temperature increases, their resistance decreases.

Bulb Failure ฀฀ A reed switch consists of two small strips of steel. When these become magnetised, they join and make a circuit. Bulb failure circuits often use a reed relay to monitor the circuit. In the circuit shown, the contacts of the reed switch will only close when electricity is flowing to the bulb being monitored.

Road Speed ฀฀ Road speed is often sensed using an inductive pulse generator. This sensor produces an AC output with a frequency, which is proportional to speed. It is like a small generator that is driven by a gear on the gearbox output shaft. This type of sensor is also used to sense engine speed from the flywheel or crankshaft.

Engine Speed ฀฀ Engine speed can be sensed in a number of ways. The Hall effect sensor however, is a very popular choice, as it is accurate and produces a square wave output with a frequency proportional to engine speed. The Hall IC produces a voltage when it is in a magnetic field. The rotating plate shown here alternately prevents and allows the magnetism to reach the IC.

Fluid Level ฀฀ Fluid levels, such as washer fluid or radiator coolant, are often measured or sensed using a float and reed switch assembly. The float has a magnet attached that causes the contacts to join when it is in close proximity. The float moves up or down depending on the fluid level.

Oil Pressure ฀฀ Oil pressure may be measured and displayed on

a gauge or, as is most common, by using a simple warning light. For this purpose, a diaphragm switch is used. As oil pressure increases, it is made to act on a diaphragm. Once it overcomes spring pressure, the contacts are operated. The contacts can

be designed to open or close as pressure reaches a set level.

Brake Pad Wear

Brake pad wear is

sensed by using a simple embedded

contact wire. When the friction

material wears down the embedded contact

Brake pads with sensor wires makes contact with

the disc to complete a circuit. Some systems use

a loop of wire that is broken when the pad wears out.

Lights in Operation ฀฀ Lights in operation can be monitored by

a bulb and simple circuit. However, note that this circuit will only indicate that the switch is on, it will not confirm that the circuit is working. A good example of this is the main beam warning light.

Battery Charge Rate ฀฀ Battery charge rate can be sensed by

a simple bulb circuit. The charge warning light is caused to go out when the alternator produces an output on one side of the bulb, which is the same as that supplied by the battery to the other side. If an equal voltage is supplied to both sides, the voltage across the warning light will be zero, and hence it will not be lit!

Summary ฀฀ A wide range of sensors is used to operate instrument displays. Sensors convert what is being measured into an electrical signal. This may be by a simple on/off operation, a changing voltage output or a change in resistance.