Before starting to check a faulty circuit, first study the circuit diagram of this circuit in order to understand what elements it consists of. The source of the malfunction can be found faster if you determine which of the elements of this circuit are working properly. If several elements or circuits fail at once, the problem is probably a blown fuse or poor grounding, since often one fuse is responsible for several circuits.
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 blown jumper, or a faulty relay. Visually check the condition of all fuses, wires (if it is possible) and connections in a faulty circuit before starting to check other elements of this circuit. If you're going to be using test equipment, use the circuit diagrams to determine which connections you need to check to find a problem.
The main instruments needed to find a fault in the electrical circuit are a voltmeter (or a 12 volt light bulb with connecting wires), a continuity tester, a battery with connecting wires and a jumper wire, preferably with a circuit breaker that can be used to connect in parallel to the circuit. Before troubleshooting using test equipment, study circuit diagrams to determine connection points.
Voltage test
A voltage test must be carried out if the electrical circuit is faulty. Connect one of the test light probes to the negative terminal of the battery or (mass) car. Connect the second probe to a connection in the circuit under test, preferably as close as possible to the battery or fuse. If the control lamp lights up, voltage is present: this means that the part of the circuit between the connection and the battery is good. Continue checking the rest of the chain in the same way. When you find the point where there is no voltage, it means that the source of the fault lies between that point and the last point where voltage was present. Most problems are caused by a bad connection. Note. Do not forget that in some circuits there is voltage only if you turn the key in the ignition switch to a certain position
Short circuit detection
One method of finding the short circuit point is to remove the fuse and connect a test light or voltmeter to the fuse terminals when all other electrical equipment on that circuit is turned off. There should be no voltage in the circuit. Move the wires from side to side and watch the control light. If it lights up, it means that somewhere in this area one of the wires is shorted, probably in the place where the insulation was worn. The same test can be carried out on any other element of the circuit, including the switch.
Checking the reliability of grounding
Carry out a grounding test to check the reliability of the connection of an electrical equipment item to (mass (car. Disconnect the battery and connect one of the wires of the continuity tester to "mass" car. Connect the second wire to the connection or ground point to be tested. If the control lamp lights up, then the grounding is in order.
Continuity Check
A continuity check is necessary to determine if there is a break in the circuit. Remove voltage from the circuit and test the circuit for continuity with a light bulb connected to the power source. Connect the light bulb wires to the ends of the circuit (or to the positive end and "mass" car); if the control lamp lights up, there are no breaks in the circuit. If the light does not come on, then there is an open somewhere in the circuit. Similarly, you can check the switch by connecting a test light to the switch terminals. After turning on the switch, the control lamp should light up.
Finding an open circuit
It can be quite difficult to visually find an open circuit, since an oxidized or poor connection of contacts is often difficult to notice. Sometimes just moving a connection wire or a wire in a wiring harness is enough to fix this problem. Unreliable operation of electrical equipment elements is also often caused by oxidized or poor connections.
Finding a fault in the electrical system seems to be a fairly simple operation, if you understand that the operation of the electrical system is based on the fact that the current flows from the battery through wires, switches, relays, fuses and burnable jumpers to the electrical equipment (light bulb, motor, etc.) and on (mass) car, from where it is fed back to the battery. Any malfunction in the electrical system is a disturbance in the flow of current from or to the battery.