Recommendation. When looking for the causes of a malfunction of any of the electrical equipment, first make sure that its fuse is in good condition and that the circuit connectors are in good contact. A common reason for the inoperability of electrical equipment is the oxidation of the terminals of the connecting blocks. In this case, they must be carefully cleaned. Pay particular attention to the connections between the negative terminals of electrical equipment and «weight» car. Often it is the lack of reliable contact with «weight» leads to electrical malfunctions.
To troubleshoot electrical equipment, you should use a tester - this is a combined electrical measuring instrument. Such devices are of several types: analog (with arrow indicator), digital (with liquid crystal display), universal (having both a pointer indicator and a liquid crystal display). When repairing a car, it is more convenient to use a digital device (or, as it is also called, a multimeter). It is compact and shows accurate values regardless of its position in space.
To check de-energized circuits, the multimeter is switched to ohmmeter mode. When measuring very small resistance (within a few ohms) it is necessary to make a correction - from the obtained value, subtract the internal resistance of the multimeter, the electrical resistance of its wires and probes (typically 0.06-0.08 ohm). To accurately determine this correction, you should switch the device to the mode for measuring small resistance values (up to 200 Ohm) and close the ends of its probes.
To check energized circuits, the multimeter is switched to voltmeter mode (with a measurement limit up to 20 V).
In addition, the multimeter allows you to measure the current consumed by the vehicle's electrical equipment (typically up to 10 A).
If it is necessary to determine only the presence or absence of voltage in a circuit section (without measurement), it is more convenient to use a special 12 V indicator light...
...or a test lamp that you can make yourself (from a car lamp with a power of not more than 4 W, soldering to it two wires with a length of at least 50 cm).
Comment. The procedure for checking the technical condition of the vehicle's electrical appliances is described in the relevant sections of the chapter.
Very often, the reason for the inoperability of electrical appliances is the oxidation of the contacts in the pads of the wiring harnesses, and to eliminate the malfunction, it is enough to clean the terminals of the pads and treat them with a special conductive grease.
If any lighting device does not work (such as headlight, turn signal, interior light and so on), first you should check if the lamp has burned out, and only then check the electrical circuits.
The algorithm for checking electrical circuits is common to all electrical appliances. First, check the fuse and relay of a non-working device. Replace the blown fuse. If, when the appliance is turned on, the fuse that protects its electrical circuit blows again, there is a short circuit in the electrical wiring that must be urgently repaired.
Warning! If you are not confident in your abilities, then contact a service station to repair electrical equipment, as unqualified repairs can lead to serious damage or fire to the car's electrical wiring.
Further troubleshooting is reduced to continuity of electrical circuits (see «Electrical equipment diagrams») and to search for faulty elements (wires, switch, device) and their replacement or repair.
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