Recommendation: When searching for the causes of a malfunction of any of the electrical equipment devices, 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 the connecting blocks are a common cause of electrical equipment failure. Clean the terminals if necessary. Check especially carefully the connection points of the negative terminals of the electrical equipment with the vehicle ground. Often, it is the lack of reliable contact with the "ground" that leads to malfunctions in the electrical equipment.
To find faults in electrical equipment, you should have a tester - this is a combined electrical measuring device. Such devices come in several types: analog, with an arrow indicator; digital, with liquid crystal display; universal - having both an arrow 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 - subtract the internal resistance of the multimeter, the electrical resistance of its wires and probes from the obtained value (usually 0.06-0.08 Ohm). To accurately determine this correction, you should switch the device to the low resistance measurement mode (up to 200 Ohm) and short-circuit the ends of its probes.
To check live circuits, the multimeter is switched to voltmeter mode (with a measurement limit of up to 20 V). The multimeter allows you to measure the current consumed by the vehicle's electrical equipment (up to 10 A).
If it is necessary to determine only the presence or absence of voltage on a section of the circuit, without measuring the value, it is more convenient to use a special 12 V light indicator...
...or a control lamp that you can make yourself (from a car lamp with a power of no more than 4 W, soldering two wires at least 50 cm long to it).
Note: The procedure for checking the technical condition of the vehicle's electrical equipment is described in the relevant sections of the chapter.