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 there is reliable contact in the connectors of its circuit. Oxidized terminals of connecting blocks are a common cause of inoperability of electrical equipment. Clean up the leads if necessary. Especially carefully check the connection points of the negative terminals of the electrical equipment with the vehicle ground. Often it is the lack of reliable contact with «weight» leads to electrical malfunctions.
To troubleshoot electrical equipment, you should have a tester - this is a combined electrical measuring instrument. Such devices are of several types: analog, with a pointer 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 at any position in space.
To check de-energized circuits, the multimeter is switched to ohmmeter mode. When measuring very low resistance (within a few ohms), it is necessary to introduce 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 of measuring low 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). The multimeter allows you to measure the current consumed by the electrical equipment of the car (up to 10 A).
If it is necessary to determine only the presence or absence of voltage in a circuit section, without measuring the value, then it is more convenient to use a special 12 V light indicator...
...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 equipment is described in the relevant sections of the chapter.