Circuit fault detection
An electrical circuit consists of an electrical element, switches, relays, motors, fuses, circuit breakers, wires and connectors that connect the electrical element to the battery and body. To assist in troubleshooting the electrical system, circuit diagrams are provided at the end of this manual.
Before attempting to determine the source of a fault, first study the relevant circuit diagram to get an idea of the elements installed in this circuit. The circle of possible sources of malfunction can be narrowed down by checking the functioning of other elements included in this circuit. If several elements or circuits fail at the same time, then the problem is obviously a fuse common to these circuits or elements, or contact with the body.
Malfunctions are usually due to simple causes such as loose or oxidized connectors, no contact with the body, blown fuses, a blown jumper or a bad relay. Visually check the condition of all fuses, wires and connectors in the failed circuit before proceeding to check the rest of the elements. Use the wiring diagrams to determine which end clamps need to be checked to find the source of the problem.
Use a tester or voltmeter to troubleshoot (LED probe); ohmmeter; battery and a set of wires with probes; cap puncture, preferably with a circuit breaker or fuse, which is used to bypass the tested wires or elements.
Unreliable contact in the electrical circuit of any of the elements (usually due to poor connection or oxidation of the contacts, or damaged insulation), you can check by shaking the wires. It is necessary to shake the wire by hand to check if the fault appears when the wire is moved. This method can reduce the range of possible. fault sources to any wire.
Along with problems due to loose wire connections, two main types of faults occur in an electrical system - an open circuit or a short circuit.
The circuit opens as a result of an open or oxidized contact in the electrical circuit, which will cause the electrical equipment to turn off.
A short circuit in a section of a circuit causes current to leak from another circuit, usually directly to the body. A short circuit is usually caused by a break in the insulation of the wires, allowing the wire to touch another wire or some grounded item, such as the body. A short circuit will usually blow the corresponding fuse.
To test for continuity, connect a circuit tester or negative voltmeter probe to the negative battery terminal or ground. Connect the second probe to the connection on the circuit under test, preferably closest to the battery or fuse. In this case, this section of the circuit must be energized from the battery (at the same time, do not forget that some electrical circuits are switched on only when the key in the ignition switch is turned to a certain position).
Switch on the circuit with the switch, then connect the tester probe to the connection closest to the circuit breaker on the side of the element being tested. If voltage is present (What do the voltmeter readings indicate?), this means that the section of the circuit between the corresponding connection and the switch has no breaks.
Continue testing the circuit in the same way. The detection of a section where there is no voltage indicates that a circuit break occurred between this point and the point of the previous test, which had voltage. Most open circuit problems are caused by a broken or loose connector.
To locate the source of the short circuit, first disconnect the load elements of the circuit (elements that consume electrical current, such as light bulbs, electric motors, heating elements, etc.).
Remove the appropriate fuse and connect the tester or voltmeter leads instead. Turn on the power in the circuit, while not forgetting that some circuits of electrical equipment are turned on only when the key in the ignition switch is turned to a certain position. If voltage is present, it means that there is a short circuit in the circuit. If there is no voltage during the test, but the fuse still blows when that circuit load is connected, this indicates a failure of the load element.
Detection of poor-quality grounding
The negative terminal of the battery is connected to «mass» -metal of the body, engine or gearbox. This means that the electrical component attachment and the bodywork are part of the electrical circuit. An insecure or oxidized fastening may cause the element to fail or malfunction. In particular, light bulbs can burn dimly (especially if at the ground point of this bulb, the grounding of some other piece of electrical equipment that is still switched on is carried out), electric motors can run slowly, and the operation of one circuit may have an imperceptible effect on the operation of another circuit. Keep in mind that many vehicles use ground wires between some parts such as the engine/transmission and the bodywork where there is no direct metal to metal contact due to soft rubber mounts or a layer of paint.
To check the reliability of the grounding of the element, it is necessary to disconnect the battery and connect one of the ohmmeter probes to a reliably grounded element. Connect another probe to the wire or body connection to be tested. The resistance shown by the ohmmeter should be zero; otherwise, check the connection as follows.
If there is no ground, disassemble the connection and clean the body area and wire terminal (or element ground surface) to bare metal. Carefully remove all traces of dirt, then use a knife to remove all paint so that there is good contact between two metal surfaces. When assembling, securely tighten the connector fastener; When connecting the wire terminal, place a serrated washer between the terminal and the body surface to ensure a secure connection. When connecting, to prevent future corrosion, apply a layer of Vaseline or silicone grease.
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