Order of execution
1. A typical electrical circuit consists of elements of electrical equipment, switches, relays, motors, fuses, fuses and wires and connectors that connect all elements to each other, the battery and "weight" car.
2. The cause of the malfunction can be found much faster if you determine which of the elements of this circuit are working properly. If several components or circuits fail at once, the problem is probably a blown fuse or poor grounding, as often one fuse protects several circuits.
3. Problems with the operation of an electrical system are usually caused by simple causes, such as oxidized or unreliable contacts, a blown fuse, a blown fuse, or a faulty relay. Visually inspect the condition of all fuses, wires, and connectors on the faulty circuit before checking other components in that circuit.
4. The main instruments needed to detect a fault in the circuit are:
- tester or voltmeter (or a 12 V light bulb with connecting wires);
- control lamp with power supply (or a continuity tester);
- ohmmeter (for measuring resistance);
- accumulator battery;
- probes with wires;
- loop wire, preferably with a circuit breaker or fuse, which can be used to test wires or electrical equipment.
5. To detect a loose connection or a short circuit (usually due to a bad or dirty connection, or damaged insulation) the wires can be shaken by hand to see if the circuit breaks when the wire is moved. In this way, you can find a point with an unreliable connector or a point where a short circuit occurs.
6. In addition to the problems associated with an unreliable connection, the electrical circuit can have two other main faults - the presence of an open circuit or a short circuit.
7. An open in the circuit can be caused by a broken wire or a loose connection in the circuit, preventing the current from flowing. An open circuit will cause a piece of electrical equipment to fail, but will not blow the fuse protecting that circuit.
8. Short circuit faults are caused by a short circuit in a circuit, which causes the current flowing in the circuit to start flowing in another circuit, and most often goes to "mass". A short circuit is usually caused by a break in the insulation, allowing the power wire to touch either another wire or a grounded item such as the bodywork. A short circuit will blow the fuse protecting the corresponding circuit.
9. Before troubleshooting or making repairs to an electrical system, be aware that different types of wires have different colors.
10. To detect an open circuit, connect one of the test light probes to the negative terminal of the battery or "mass" car.
11. Connect the second probe to a connection in the circuit under test, preferably located as close as possible to the battery or fuse.
12. Apply voltage to the circuit. Do not forget that in some circuits, voltage is supplied only when the key in the ignition switch is turned to a certain position.
13. If voltage is present (what will be indicated by a lit control light or voltmeter readings), this means that the part of the circuit between the connection and the battery is good.
14. Continue checking the rest of the circuit in the same way.
15. When a point is found where voltage is absent, this means that the source of the fault lies between this point and the previous point where voltage was present. Most of the problems are due to a bad connection.
16. The negative battery terminal is connected to "mass" vehicle - the engine/gearbox metal and the vehicle body - and most electrical equipment systems are designed so that only one supply wire is connected to a piece of equipment and the current is returned through the metal of the vehicle body. This means that the fastening of the electrical equipment element and the car body are part of the electrical circuit. Therefore, a poor or oxidized fastening can cause a large number of problems in the electrical equipment system: from complete failure of the circuit to unreliable operation. In particular, light bulbs can burn dimly (especially if another circuit is switched on using the same ground point), engines (e.g. wiper motors or radiator fan) may operate slowly and turning on one circuit may affect the operation of another circuit. Note that many vehicles use bonding ground strips between various parts of the vehicle, such as between the engine/transmission and the body, i.e. usually when there is no metal contact between the elements due to the use of rubber fasteners, etc.
17. To check the reliability of grounding, disconnect the battery and connect one of the ohmmeter probes to "mass" car. Connect the second probe to the wire or ground point you want to test. The resistance recorded by the ohmmeter must be zero, otherwise, check the connection as follows.
18. If you think the connection is not good, disassemble the connection and clean to bare metal the contact surface and the wire terminal or the surface of the grounding element. Remove all dirt and corrosion, then use a knife to remove a layer of paint in order to obtain a reliable metal-to-metal bond. When assembling, fix the connection securely; When installing the wire terminal, use toothed washers between the terminal and the body. After connection, apply a layer of Vaseline or silicone grease to the connection to prevent corrosion.
Circuit breakers
Fuses are used to break the circuit when the current reaches a certain value, in order to protect elements and wires that can be damaged by too much current. A sudden increase in current is usually caused by a fault in the circuit, most often a short circuit.
The designations of the circuits protected by fuses are indicated on the cover of the fuse box.
Turn off the relevant circuit before removing a fuse (or ignition), then remove the fuse from the contacts. A wire should be visible inside the fuse; if the fuse is blown, the wire will be broken or melted.
Always use fuses of the required capacity. Never use a fuse of a different capacity and do not replace it with something else. Do not replace the fuse more than once without correcting the source of the problem. The current protected by the fuse is indicated on the top of the fuse: note that the fuses have different colors for easy identification.
If a fuse blows immediately after replacement, do not replace it again until the cause of the problem has been identified and corrected. In most cases, the fault is caused by a short circuit caused by poor insulation. If the fuse is protecting multiple circuits, try to find the circuit that is causing the fuse to blow, including each circuit in turn (if it is possible). Always have a set of spare fuses of different ratings in your car. They must be fixed at the base of the fuse box.