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Fault Detection
A warning  Read the precautions (see. Section 14) before you start.
The following tests are intended to verify the basic electrical circuits and they should not be used to scan sensitive electrical circuits (such as the ABS), particularly if the circuit is an electronic control unit.
A typical electric chain consists of an element of electrical equipment, switches, relays, motors, fuses, fusible jumpers or circuit breakers and cables and connections, which connect all the elements together and connect them to the battery and the (weight) of the car. In order to simplify the process of troubleshooting, in Section 14.20 shows the electrical circuit of the car's electrical system. Before starting the test the affected circuit, first examine the concept of the chain in order to understand what elements it is composed.
Source faults can be found quickly, if it is determined which of the elements of this chain work normally.
If a failure of some elements or chains, the problem probably lies in a blown fuse or bad grounding as frequently one safety lock is responsible for several circuits.
Problems with the operation of the electrical system are usually caused by the simple reasons, such as oxidised or unreliable contacts, blown fuse, burned fusible link or the faulty relay (the description of the test operation switch, see. In section 14.3).
Visually check the condition of all safety locks, wires and connections in the affected circuit before checking other elements of this circuit.
If you are going to use test instruments, use the concepts in order to determine which connections should be checked for fault detection. The main instruments necessary for finding fault in the circuit of electrical equipment, are a voltmeter (or a bulb on 12 Volt with connecting wires), a device for checking the integrity of the chain, an ohmmeter (to measure resistance), battery with connecting wires and cap wire, preferably with a circuit breaker, which can be used for parallel connection to the circuit.
Before you start finding fault with the use of test equipment, study the concepts to determine the point of connection. To locate poor connections or short-circuit point (usually because of a bad connection or dirty, or damaged insulation) wires can be shaken by hand to see if the circuit does not go out of operation at wire movement. In this way, a point can be found with a fragile compound or a point at which short circuit occurs. This method of scanning can be used along with the rest of the tests described in the following subsections. In addition to problems associated with the bad connection, the electrical circuit may have two other major problem - the presence of discontinuity in the circuit or short circuit. The gap in the circuit can be caused by rupture of any wire or absence of the compound anywhere in the chain, which would prevent the flow of current. The break in the chain will cause the failure of any item of electrical equipment in the work, but will not cause an open fuse to the circuit. Problems with the short circuit caused by the closure elsewhere in the chain, which leads to the fact that the current flowing through the circuit begins to flow in the other circuit, and more often goes on (weight). Short circuit is usually caused by rupture of isolation, allowing the power supply wires to touch any other conductor or a grounded element, such as a body. Short circuit causes a blown fuse corresponding chain.
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