What is needed to find faults?
Finding the problem when complex automotive systems go wrong is easy, if you have the necessary knowledge. This knowledge is in two parts:
● understanding of the system in which the problem exists;
● the ability to apply a logical diagnostic routine. It is also important to be clear about two definitions:
● symptom(s) what the user/operator/repairer of the system (vehicle or whatever) notices;
● fault the error in the system that causes the symptom(s).
‘If it is not broken then do not go to the trouble of repairing it,’ is the translation of this main section heading! It’s a fair comment but if a system is not operating to its optimum then it should be repaired. This is where the skills come in to play.
It is necessary to recognise that something is not operating correctly by applying your knowledge of the system, and then by applying this knowledge further and combining it with the skills of diagnostics, to be able to find out why.
Each main chapter of this book includes a basic explanation of the vehicle system followed by diagnostic techniques that are particularly appropriate for that area. Examples of faultfinding charts are also included. In the main, references will be to generic systems rather than to specific vehicles or marques. For specific details about a particular vehicle or system the manufacturer’s information is the main source. Alternatively ‘Autodata’ produce a fine range of books;
The knowledge requirement and the necessity for diagnostic skills are further illustrated in the next chapter.
Finding the problem when complex automotive systems go wrong is easy, if you have the necessary knowledge. This knowledge is in two parts:
● understanding of the system in which the problem exists;
● the ability to apply a logical diagnostic routine. It is also important to be clear about two definitions:
● symptom(s) what the user/operator/repairer of the system (vehicle or whatever) notices;
● fault the error in the system that causes the symptom(s).
‘If it is not broken then do not go to the trouble of repairing it,’ is the translation of this main section heading! It’s a fair comment but if a system is not operating to its optimum then it should be repaired. This is where the skills come in to play.
It is necessary to recognise that something is not operating correctly by applying your knowledge of the system, and then by applying this knowledge further and combining it with the skills of diagnostics, to be able to find out why.
Each main chapter of this book includes a basic explanation of the vehicle system followed by diagnostic techniques that are particularly appropriate for that area. Examples of faultfinding charts are also included. In the main, references will be to generic systems rather than to specific vehicles or marques. For specific details about a particular vehicle or system the manufacturer’s information is the main source. Alternatively ‘Autodata’ produce a fine range of books;
The knowledge requirement and the necessity for diagnostic skills are further illustrated in the next chapter.
Figure 1.1 shows a diagnostic procedure in action!
1.1.2 Heavy or light vehicles?
An important note about diagnostics is that the general principles or techniques can be applied to any system, physical or otherwise. As far as heavy or light vehicles are concerned then this is definitely the case. As discussed earlier, there is a need for knowledge of the particular system, but diagnostic skills are transferable.
1.2 Safe working practices
1.2.1 Introduction Safe working practices in relation to diagnostic procedures and indeed any work on a vehicle are essential – for your safety as well as that of others.
You only have to follow two rules to be safe:
● use your common sense – don’t fool about;
● if in doubt – seek help.
Further, always wear appropriate personal protective equipment (PPE) when working on vehicles.
1.1.2 Heavy or light vehicles?
An important note about diagnostics is that the general principles or techniques can be applied to any system, physical or otherwise. As far as heavy or light vehicles are concerned then this is definitely the case. As discussed earlier, there is a need for knowledge of the particular system, but diagnostic skills are transferable.
1.2 Safe working practices
1.2.1 Introduction Safe working practices in relation to diagnostic procedures and indeed any work on a vehicle are essential – for your safety as well as that of others.
You only have to follow two rules to be safe:
● use your common sense – don’t fool about;
● if in doubt – seek help.
Further, always wear appropriate personal protective equipment (PPE) when working on vehicles.
The following section lists some particular risks when working with electricity or electrical systems, together with suggestions for reducing them. This is known as risk assessment.
1.2.2 Risk assessment and reduction
The following table notes some identified risks involved with working on vehicles. It is by no means exhaustive but serves as a good guide.
Identified risk Reducing the risk
1.2.2 Risk assessment and reduction
The following table notes some identified risks involved with working on vehicles. It is by no means exhaustive but serves as a good guide.
Identified risk Reducing the risk
- Battery acid Sulphuric acid is corrosive so always use good PPE – in this case overalls and if necessary rubber gloves. A rubber apron is ideal, as are goggles if working with batteries a lot
- Electric shock Ignition HT (high tension, which simply means high voltage) is the most likely place to suffer a shock, up to 25 000V is quite normal. Use insulated tools if it is necessary to work on HT circuits with the engine running. Note that high voltages are also present on circuits containing windings due to back emf (electromotive force) as they are switched off; a few hundred volts iscommon. Mains supplied power tools and their leads should be in good condition and using an earth leakage trip is highly recommended
- Exhaust gases Suitable extraction must be used if the engine is running indoors. Remember it is not just the carbon monoxide (CO) that might make you ill or even kill you, other exhaust components could cause asthma or even cancer
- Fire Do not smoke when working on a vehicle. Fuel leaks must be attended to immediately. Remember the triangle of fire – (heat/fuel/oxygen) – don’t let the three sides cometogether
- Moving loads Only lift what is comfortable for you; ask for help if necessary and/or use lifting equipment.As a general guide, do not lift on your own if it feels too heavy!
- Raising or Apply brakes and/or chock the wheels and lifting vehicles when raising a vehicle on a jack or drive on lift. Only jack under substantial chassis and suspension structures. Use axle stands in case the jack fails Running Do not wear loose clothing; good overalls engines are ideal. Keep the keys in your possession when working on an engine to prevent others starting it. Take extra care if working near running drive belts
- Short circuits Use a jump lead with an in-line fuse to prevent damage due to a short when testing.Disconnect the battery (earth lead off first and back on last) if any danger of a short exists. A very high current can flow from a vehicle battery, it will burn you as well as the vehicle
- Skin problems Use a good barrier cream and/or latex gloves.Wash skin and clothes regularly
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