Contents: General description 🠛 Finding a broken circuit 🠛 Finding a short circuit 🠛 Finding a short to ground 🠛
General description
1. An electrical circuit consists of electrical components, switches, relays, motors, fuses, reverse current relays, and wiring. To accurately locate a fault in an electrical circuit, electrical connection diagrams are provided at the end of this Section.
2. Before diagnosing an electrical circuit, first study the electrical connection diagram. If multiple components fail at the same time, the problem may be with a fuse or ground.
3. Electrical faults are usually caused by simple reasons, corroded connections, faulty grounding, blown fuses or a faulty relay. Visually inspect the condition of all fuses, wires, and connections in the application circuit before testing components. Use electrical wiring diagrams to pinpoint the location of the fault.
4. The basic tools required to troubleshoot an electrical circuit are a tester or voltmeter, a stroboscope, an ohmmeter, a battery, and a set of load resistors. Before troubleshooting, use the wiring diagram to determine where to make connections.
5. To find the break, move the electrical wiring. This method can be used in combination with other tests described in the following subchapters.
6. Besides problems caused by loose connections, two types of faults can occur in an electrical circuit - open or short circuit.
7. As a result of a circuit break, the component stops working, but the corresponding fuse will remain intact.
8. A short circuit causes current to flow through a different path, usually to ground. A short circuit typically occurs due to insulation failure, causing wires to touch each other or a grounded component (for example, bodies). When a short circuit occurs, the corresponding fuse usually blows.
Finding a broken circuit
9. Connect one lead of the tester or voltmeter to the negative battery terminal or ground.
10. Connect the other wire to the circuit being tested, preferably closer to the battery or fuse.
11. Turn on the circuit being tested, keep in mind that some circuits are only energized when the key is in a certain position in the ignition switch.
12. If voltage is present, this means that the circuit section between the corresponding connector and the battery is OK.
13. Continue checking the remaining sections of the chain in the same manner.
14. When no voltage is registered at any point, the problem must be between that point and the previous point with voltage that was checked.
Finding a short circuit
15. First, disconnect the load from the circuit being tested (components that are powered by the circuit: for example, lamps, motors, heating elements, etc.).
16. Remove the appropriate fuse and connect a tester or voltmeter to the fuse socket.
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17. Turn on the circuit being tested, keep in mind that some circuits are only energized when the key is in a certain position in the ignition switch.
18. If voltage is present, there is a short circuit in the circuit.
19. If there is no voltage, but the fuse still blows when the load is turned on, this indicates a load fault.
Finding a short to ground
20. The negative battery terminal is connected to ground - the engine/transmission block and the car body - and most systems are designed to be connected by wire to positive power only. This means that the component mount and housing are part of the circuit. Corrosion of the mounting bracket may be the cause of an electrical circuit malfunction. In particular, the lights may burn dimly (especially when another circuit is connected, sitting on the same ground point), motors (for example, a windshield wiper or a radiator fan) may rotate slowly, and the functioning of one circuit may indirectly affect the other. Please note that many vehicles use ground straps between certain components, such as between the engine, transmission, and body, where there is typically no metal-to-metal connection due to flexible rubber pads, etc.
21. Check to see if the component is properly grounded, then disconnect the negative battery cable and connect one lead of the ohmmeter to a good ground and the other lead to the wire or ground terminal being tested. The resistance should be zero; if this is not the case, check the connection as follows.
22. If a faulty ground contact is suspected, disassemble the connection and clean the body, terminal, or ground contact surface to bare metal. When assembling, tighten the fasteners securely. Then lubricate the connection with Vaseline or silicone grease, or cover it with a special sealant.