Before troubleshooting an electrical circuit, first study the appropriate wiring diagram and get a complete understanding of the components included in this circuit. The search for possible sources of malfunction is easier if you make sure that other components included in this circuit are working. If multiple components or circuits fail at the same time, there is a problem. likely to be connected to a fuse or ground connection.
Faults in electrical circuits usually come from simple causes such as bad connectors, poor grounding, a blown fuse, or a faulty turnip. Before. To begin checking circuit details, inspect the condition of all fuses, wires, and connectors on the faulty circuit.
Use the wiring diagrams to determine the order in which to test the electrical target.
Basic tools for troubleshooting electrical circuits include a tester or voltmeter (a 12 volt test light may also be used for some tests); ohmmeter (to check the circuit for open wires): battery: jumper wire, preferably with a fuse that can be used. to bypass wires or electrical components being tested. Before working with the instruments, study the wiring diagram to determine the points where any measurements should be made.
Voltage test
A voltage test is needed if the circuit starts to malfunction. Connect one lead of the voltmeter to the negative battery terminal or a good grounding point. Connect the second wire to the component being tested, preferably closer to the battery or fuse. If voltage is present (or the control lamp lights up), then part of the circuit from the battery to the connection point of the voltmeter is working. Continue checking the circuit at short intervals. When you reach the point where there is no voltage, find the fault between the last two points of connection of the voltmeter. Most faults of this kind are due to poor contacts.
Note. Remember that voltage in some circuits is only present when the ignition key is turned to "Accessory" or "Run".
Circuit short detection
One way to check is as follows. Remove the appropriate circuit fuse and connect the terminals of a tester or voltmeter to the fuse terminals. In this case, there should be no voltage. Move the wiring while watching the light bulb (or voltmeter). If the lamp lights up, this indicates a short circuit in the tested sing (most often a short circuit occurs in places where the insulation is worn). In the same way, you can check the circuit by removing any of its components, even a switch.
Ground Fault Detection
To check if a component is well grounded, disconnect the battery and connect one ohmmeter lead to a good grounding point. Connect the second wire of the ohmmeter to the point to be tested on the component. The ohmmeter should show zero resistance; if not, reconnect the component to ground.
Continuity Test
Continuity testing is about finding and detecting breaks in the circuit. With an open circuit, the continuity test is carried out using a test lamp with a power source. Connect a test light to both ends of the circuit to be tested. If the light comes on, then the circuit is good. If the light does not come on, then the circuit is open. This procedure is usually used to check the health of switches. The wires of the control light are connected to the terminals of the switch. When the switch is turned on, the lamp should light up.
Open Circuit Detection
The difficulty that arises when searching for open circuits is that, as a rule, they are associated with corrosion of the contacts in the connectors. Try wiggling the connectors or wiring harnesses first (most often, the connection in the circuit is restored).
Troubleshooting is made easier if you remember that all electrical targets start at the battery, go through fuses, relays, wires, connectors, loads (pumps, electric motors, etc.), and then through the case back to the negative terminal of the battery. Sometimes the malfunction is due to poor contact of the wires with the battery terminals.
Connections
Most car circuit connections are made in the form of multi-pin connectors. The halves of the connectors are made of plastic and are connected to each other with clamps. Sometimes half connectors (especially large) bolted together.
To disconnect the connectors, you need to use a screwdriver to take aside the plastic retainer and disconnect one half of the connector from the other. Always pull on the connector housing only and never on the wiring harness (this can lead to a broken wire or contact in the connector). Before disconnecting a connector, examine it carefully. Many connectors have several latches that are not always conspicuous. All connectors consist of a half in which there are pins (connector type "dad") and half, in which there are holes (connector type "Mother"). On the wiring diagrams, these connectors are labeled accordingly, which makes it easier to identify the wires. Both halves of the connectors are mirror symmetrical to each other (i.e. the left side of one half of the connector is the right side for the other half). If you insert the tester's probe into a connector terminal of type "Mother", ensure that the probe makes good contact with the terminal. Be careful not to damage the terminal (this may lead to poor contact in this terminal, and the fault may occur later).
Very often it becomes necessary to check the continuity of the circuit with the connector connected. In this case, carefully insert a straight thin rod from the back of the connector, then connect the tester to it. If you try to insert the tester's probe, it may break the connector (pic. 2.15).