If any component of the vehicle fails, find the electrical circuit that includes this component and follow it step by step to determine the possible reasons for the failure of electrical current to reach this component.
Very often problems arise simply due to the lack of contact in the wire connectors, caused by oxidation or unreliable connection of the latter, a blown fuse, a poor connection to the "ground" due to oxidation of the connecting wires, or a relay failure.
Therefore, before checking and replacing units and parts of electrical equipment, carefully check the circuit and eliminate the listed causes of failure.
Most tests are performed with a tester or voltmeter. You can also use a 12-volt test light with two wires. Before troubleshooting, study the wiring diagram carefully to get an idea of where in the circuit the device or test light should be connected.
Sometimes, to localize a failure of electrical equipment, it is enough to move the wiring with your hand and use a device to determine the appearance of voltage on the problematic section of the circuit. In addition to poor contact in electrical connections, the causes of failure are often wire breaks or short circuits, i.e. connection to the "ground".
If there is a break in the circuit, the electrical current is interrupted, but this does not cause the fuse to blow.
In case of a short circuit, which occurs due to damage to the wire insulation (aging, pinching of the wire at the points of contact with the body), the electric current becomes very large, which causes the fuse protecting the corresponding section of the circuit to burn out.
To detect an open circuit, follow these steps:
- connect the tester lead or the negative terminal of the voltmeter to the negative terminal of the battery. A reliable contact with the body can be used for this (not covered with paint);
- connect the other lead of the device to the contact connector in the circuit being tested, preferably the one closest to the positive terminal of the battery or the fuse;
- apply voltage to the circuit being tested (please note that some circuits are only powered when the key is in a certain position in the ignition switch) and by the presence or absence of voltage on the device, make sure that the circuit being tested is working properly or is broken;
- continue checking the circuit using the same method until you find the break point;
- eliminate the defect in the chain, the main cause is corrosion of the connections or poor contact in them.
To detect a short circuit in a circuit, follow these steps:
- disconnect, having identified from the electrical diagram, the current consumers - lamps, heating elements, electric motors, etc.;
- remove the appropriate fuse from the unit and connect the instrument wires to the fuse socket contacts;
- apply voltage to the circuit being tested (please note that some circuits are only powered when the key is in a certain position in the ignition switch) and visually determine the presence or absence of a reading on the device;
- the presence of a reading on the device indicates a short circuit in the circuit, the absence of a reading means a malfunction in the composition of the electric current consumers.
The car's electrical equipment is made using a single-wire circuit, i.e. the negative terminals of the vast majority of electrical consumers are connected to the "ground", which acts as the second wire. The engine block and gearbox are connected to the body "ground" by braided copper buses, which are secured with bolted connections. Very often, corrosion spots appear in these connections, caused primarily by the effect of reagents for treating streets in the winter. Corrosion worsens the electrical conductivity of the circuits, which, in addition to direct failure in operation, often leads to a decrease in the rotation speed
shafts of electric motors, such as windshield wipers or heater fans. Corrosion in the connections explains the dim glow of lamps and the influence of one electrical circuit on the operation of another.
To check the reliability of the contact with the "ground" of a specific consumer, disconnect the wires from the battery, then connect the tester in the ohmmeter mode to the body and the consumer being tested. If there is good contact, the ohmmeter should show zero.
Otherwise, disassemble the connection of the unit being checked, clean the contact point on the body and the contact surface of the consumer housing (or the tips of the wire connecting to the "ground") to bare metal. Assemble the connection, carefully tightening the fasteners. To prevent corrosion of the connection, lubricate it from the outside with technical petroleum jelly or silicone grease.
Original publication on the website RENAULTBOOK.ru