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Search of causes of failures of electrical equipment
 | These procedures permit a common diagnosis of the main electric circuit, but should not be used to verify the already fragile electrical systems, in particular, includes in its membership the electronic control modules! |
Overview A typical electric circuit consists of a power consumer (work item), a set of switches, relays, actuators of electric motors, fuses, fuse links / circuit breakers, relevant to the work of the element, and the connecting wiring, its contact plugs and connectors. In order to facilitate the implementation of diagnostic procedures at the end of the Guide lists Wiring diagrams. Before embarking on the search for the causes of failure of the failed consumer of electricity, carefully read the relevant circuitry, try as clearly as possible to imagine a principle of the elements belonging to the suspect circuit. The list of possible causes of failure can be minimized by delisting properly functioning components related to the circuit under test. With the simultaneous operation of multiple violations of the components, the most likely cause of failure is the failure of the total for the corresponding circuit fuse / fuse or a ground fault. The most common electrical failure is easily explained reasons, such as oxidation or loose terminal connections, the failure of the fuse or the fuse, failure relays, etc. Before embarking on the search for internal defects actually failed component, carefully check the condition of all relating to his operation of fuses, connectors and connecting wires. To determine the list of sites to be inspected and pin connectors, read the appropriate wiring diagram (see. Wiring diagrams). Among the diagnostic tools, most often used to detect electrical failures, should include a universal measuring circuit / voltmeter (for some tests suitable as an ordinary 12-volt bulb with a set of connecting cables), bulb-probe with individual power supply (sometimes also called a conductivity meter ), ohmmeter, power supply with a set of connecting cables, as well as a set of jumper cables, equipped with various types of connection terminals and - preferably - a built-in circuit breaker or fuse (to bypass the chain of suspicious areas or electrical components). Before resorting to the use of diagnostic equipment, carefully read the wiring diagram of the corresponding components of the circuit (see. Wiring diagrams). In identifying the causes of the wearer's unstable failure (violations of this kind usually are related to the oxidation of contact plugs, or loose terminal connections wiring) can be made simple test circuit performed by twitching of various parts of the wiring of the corresponding circuit, which resulted in localized defective segment of a chain . This check can be performed in conjunction with any of the following in the respective sections. In addition to the problems associated with the violation of the quality of the electrical connections to the most frequently occurring and the likely failure of electric circuits should include breaks and short-circuit. Open circuit typically caused by mechanical damage to the electrically conductive cores or disconnecting the terminals, resulting in the opening of the electric circuit and stop the circulation of electric current therein. As a result, open-circuit component of its work ceases to function, however, appropriate fuses / fuse-links do not fail. Short circuit design called an unintended closure of its electrical circuit. When this current begins to circulate through the shortest path, in most cases, leaving the mass. Short circuits are mostly related to the violation of the integrity of the insulation of the wiring in the mandatory lead to failure of the relevant fuse / fuse-links. Check presence of voltage in the circuit | - Checking tension among the standard tests in the event of any consumer of electricity. Connect one of the wires ("-") the chain meter / voltmeter to the negative terminal of the battery, or any of properly grounded outlets on the chassis / engine. The second wire unit is connected to terminal connections checked the circuit, preferably closest to the battery or fuse. Apply power to the circuit. Do not forget that some chains are supplied only in certain positions of the ignition switch. If the voltage occurs (light meter is activated, or the display is fixed corresponding to the reading of the voltmeter), then cut the connection between the inspected terminal connection and the battery is OK.
- Continue to check in the same spirit, alternately moving from one terminal to another circuit connection in the direction of the battery / fuse. The faulty section of the circuit will be located between the point at which the instrument registers the presence of voltage and the nearest terminal connection technologies tested serviceable. The most common cause of failure is broken wiring or oxidation / loose contact element.
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Search the short-circuit | - Firstly disconnect the customer (s) under test electric circuit (power consumers or payload circuit are called components on the functioning of which is spent the circulating current in the circuit, such as lamps, electric motors, heating elements, etc.). Remove the fuse that protects the circuit under test, and connect it to the mounting terminals bulb-probe or voltmeter. Apply power to the circuit - remember that some of the circuits are supplied only in certain positions of the ignition switch. If the voltage at the terminals of the fuse occurs, hence the circuit is short-circuited, - tug wiring as short circuit may be caused by the failure of its insulation and wear unstable. If pressure is absent, however, after replacing the fuse continues to blow when power is applied to the circuit, so there is a defect in the internal user (s) of electricity, switch or wiring insulation.
- Alternatively, the test can be performed with an ohmmeter: Disconnect all the connectors of the suspect part of the circuit and start to connect the ohmmeter between each of the terminals and the ground, check the meter of having conductivity (zero display) indicates a short to ground wiring connected to the terminal under test connector .
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Search disorders Ground The negative terminal of the battery is grounded to the "masses", which serves as a metal powertrain, chassis and car body elements. Electrically mostly electrical circuits are constructed in such a way that the wiring is only used to supply power to the consumer from the positive terminal of the battery, the current returns to the battery is carried on the metal mass. This means that the fixings power consumers forming part of a return circuit. In view of this situation, loose or corroded support members of the working circuit component entails a violation of serviceability of functioning of the circuit (from the most recent complete failure to partial failure of various parts of the chain). In particular, due to the weakening of fasteners can decrease the brightness of lighting (in particular with a common ground with the other loop), or the rotation speed of the motor (for example, a drive wiper or cooling fan). At the same time the failure of one circuit can cause malfunction of another, seemingly unrelated to the failed. Please note that on many cars some nodes are interconnected by special buses ground. Such tires are used when there is no direct metal to metal contact blocks due to equipment supports flexible rubber bushings (as, for example, supports the suspension of the power unit). | - To check the health of the ground component, disconnect the battery and connect one ohmmeter lead obviously a properly grounded point of the car. The second wire gauge to connect the grounding point under test component. The device should fix the zero resistance, otherwise you should check that the electrical connections (see. Below).
- If there is suspicion of violation of the quality of the connection terminal, disassemble the contact assembly ground and smooth out to pure metal mating surfaces of the terminals. Try to completely remove all traces of corrosion and dirt, and then scrape off the paint with a knife, ensuring unambiguous contact metal surfaces. When assembling the unit, take care of the strength of a tightening of fixture. Between terminals of electrical contacts and weight to guarantee the quality of electrical connections lay the washer with a notch. In order to avoid corrosion development in the future, cover the docked terminal connections with acid-free Vaseline or silicone grease. Good agents are also spray to seal the components of the ignition system and moisture repellent grease.
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Search continuity Unstable failures electricity consumers are most likely to involve a violation of the quality of terminal connections due to oxidation or loosening of fasteners. Often cast component in working condition, is simply to pull the appropriate wiring harness / electrical connector. The easiest way to find an open circuit is to check its working areas for the presence of conduction. Disconnect the power supply circuit and use equipped with autonomous power source meter. Connect the meter to the two outputs of the circuit under test (power supply terminal and a good ground point). If the device detects the presence of conductivity (zero resistance / operation of the lamp-sampler), therefore, the circuit under test plot is serviceable. Otherwise, there is a break. Similarly, the same method can be checked up serviceability of functioning of the circuit breakers. Electrical connection - general information Most of the pin connectors onboard electric circuits are made of plastic and are multicontact. Reliability joint halves of the connectors is provided by snap-locking tabs mounted in the plug latches. Large connectors, such as some of the located under the dashboard of a vehicle, often bonded is passed through a central portion of the plug through bolts. To disconnect equipped with plastic clip connector is usually used a small screwdriver, which should be carefully squeeze locking tabs (after carefully review the design mated connector - often determine the method of fixing parts to the eye is not easy, and some connectors are equipped with multiple locking elements). Always pull the plug, but in any case not at the wiring harness, to prevent accidental damage to the connector mounted in the terminals. Connectors always consist of two sections, one of which terminals includes terminals inside the other. In the study of diagramming connector try to first determine which of its sections shown in the illustration, - connected to a harness or attached to the component. Remember that one section of the terminal connector always placed a mirror in relation to the other terminals. When checking for conduction between the connector terminals or measuring voltage between any of the terminals and the "weight" Always connect meter probes to the terminals on the rear (BCF) side of the corresponding section of the connector.  | If necessary, use a miniature probes design, or enter into a straightened paper clip connector to which you can then connect a wire gauge using a clamp-type "crocodile". |
 | Measurement of the voltage across the relay terminals mated electrical connector is made by introducing the probe meter (1) in the rear side of the terminal connector; when the sealed design of the connector the tester can be connected with the terminal side connector by means of a miniature probe design (2) |
If the connector has a sealed construction, the meter can be connected to the terminal side of the connector, however, in such a situation should be particularly careful to avoid damaging the terminals.
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