Caution: The procedures described below can be used to troubleshoot simple electrical circuits not related to electronic control circuits. In addition, they must be made carefully so as not to accidentally cause a short circuit, which can easily lead to the failure of expensive electronic systems!
A typical electrical circuit consists of an electrical consumer (working component), a set of switches, relays, actuator motors, fuses, fuses / circuit breakers related to the operation of this component, as well as connecting wiring, its contact terminals and connectors. In order to facilitate the implementation of diagnostic procedures at the end of the manual, wiring diagrams of various vehicle electrical systems are given. Before starting to search for the reasons for the failure of a failed electrical consumer, carefully study the corresponding electrical circuit, try to imagine as clearly as possible the principle of operation of the components that make up the suspect circuit before resorting to the use of diagnostic equipment. The compilers of this Guide recommend, at the slightest doubt in their own abilities, to seek help from specialists.
The most common reasons for failures are:
- Weakening of terminal connections or their oxidation;
- Failure of a fuse or fuse;
- Breakage of wires during maintenance and repair work (an open in the electrical circuit caused by other external causes is extremely rare);
- A short circuit that occurs, as a rule, in connection with a violation of the integrity of the insulation of the electrical wiring, which necessarily leads to the failure of the corresponding fuses / fuses;
- Internal malfunctions of electricity consumers or other intermediate elements of the electrical circuit.
The easiest way to diagnose is a visual inspection. Before proceeding to deeper and more complex checks, inspect the most likely places for a malfunction to occur - battery terminal clamps, fuse mounting blocks, open sections of wiring harnesses and their attachment points in intermediate clamps, also check the serviceability of electric lamps.
The accompanying signs can also suggest the reason for the refusal.
Weakening of contact in terminal connections or their strong oxidation leads to unstable failures and is often accompanied by a voltage drop in the corresponding section of the circuit - control lamps and lamps of lighting devices burn at full heat. The simplest circuit test, performed by twitching various sections of the wiring of the corresponding circuit. To eliminate oxidation of the contact terminals of the electrical wiring plug connectors, disconnect and reconnect the connectors several times. Strong oxidation must be removed with special tools, sandpaper or industrial alcohol. A short circuit in the circuit leads to a constantly repeated blown fuses / fuses.
An open circuit leads to a permanent failure, usually for no apparent reason. The fuses remain intact, external traces of damage are almost imperceptible. Try to remember if any operations have been carried out inside the engine compartment or other compartments of the car since the last proper functioning of the corresponding system. Carefully inspect the wiring, gently pull the wires in order to detect a break. If the fuse of this system burned out, and after its replacement, the functioning of the system did not resume, most likely any element included in this circuit failed.
You can find the cause of the failure using simple diagnostic equipment. Such equipment includes a universal circuit meter / voltmeter (a 12-volt lamp with a set of connecting wires will also work for some tests), probe lamp with individual power supply (sometimes also called a conductivity meter), an ohmmeter, a power supply with a set of connecting wires, as well as a set of jumper wires equipped with various types of connecting terminals and, preferably, a built-in circuit breaker or fuse (for shunting suspicious sections of a circuit or electrical components). However, you must always remember that improper connection of diagnostic equipment or poor knowledge of electrical circuits and the basics of electrophysics can lead to failure of other electrical circuits and consumers. It is better to entrust testing of modern car systems to service station specialists who have the necessary skills and have all the necessary equipment at their disposal.
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