Warning: The following procedures can be used to troubleshoot simple electrical circuits that do not involve electronic control circuits. However, they must be performed with care to avoid accidentally causing a short circuit, which can easily damage expensive electronic systems!
A typical electrical circuit consists of an electrical consumer (working component), a set of switches, relays, actuators, fuses, fuses/circuit breakers related to the operation of this component, as well as connecting electrical wiring, its contact terminals and connectors. In order to facilitate the diagnostic procedures, the electrical connection diagrams of the various systems of the vehicle's electrical equipment are provided at the end of the Manual. Before starting to search for the causes of failure of a failed electrical consumer, carefully study the corresponding electrical diagram, try to imagine as clearly as possible the operating principle of the components included in the suspected circuit before resorting to the use of diagnostic equipment. The authors of this Manual recommend that if you have the slightest doubt in your own abilities, seek help from specialists.
The most common reasons for failure are:
- Loosening or oxidation of terminal connections;
- Fuse or fuse link failure;
- Wire breakage during maintenance and repair work (a break in an electrical circuit caused by other external factors is extremely rare);
- A short circuit, which usually occurs due to a breach in the integrity of the insulation of electrical wiring, which inevitably leads to the failure of the corresponding fuses/fuse links;
- Internal faults of electrical consumers or other intermediate elements of the electrical circuit.
The simplest diagnostic method is a visual inspection. Before proceeding to more in-depth and complex checks, inspect the most likely places where the fault may occur - battery terminal clamps, fuse mounting blocks, open sections of wiring harnesses and their attachment points in intermediate clamps, and also check the serviceability of the electrical lamps.
The reason for the refusal may also be suggested by accompanying symptoms.
Loose contacts 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 lighting fixtures burn at half power. The simplest check of the circuit is carried out by twitching various sections of the electrical wiring of the corresponding circuit. To eliminate oxidation of the contact terminals of the plug-in connectors of the electrical wiring, disconnect and reconnect the connectors several times. Strong oxidation must be removed using special devices, sandpaper or technical alcohol. A short circuit in the circuit leads to constantly recurring burnout of fuses/fuse links.
A break in the circuit leads to a permanent failure, usually without any apparent reason. Fuses remain in good condition, external traces of damage are almost invisible. Try to remember whether any operations were performed inside the engine compartment or other sections of the car since the last time the corresponding system functioned properly. Carefully inspect the wiring, carefully pull the wires to detect a break. If the fuse of this system has burned out, and after replacing it, the system does not function again, most likely some element included in this circuit has failed.
The cause of the failure can be found using simple diagnostic equipment. Such equipment includes a universal circuit meter/voltmeter (for some tests, a 12-volt lamp with a set of connecting wires will also work), a test lamp with an individual power source (sometimes also called a conductivity meter), an ohmmeter, a power supply with a set of connecting wires, and a set of jumper wires equipped with various types of connecting terminals and, preferably, a built-in circuit breaker or fuse (to bypass suspected circuit sections or electrical components). However, it is always necessary to remember that incorrect connection of diagnostic equipment or poor knowledge of electrical circuits and basics of electrophysics can lead to failure of other electrical circuits and consumers. Testing of modern car systems is best left to service station specialists who have the necessary skills and have all the necessary equipment at their disposal.
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