Before attempting to repair any electrical circuit malfunction, first study the relevant circuit diagrams. Suspicious points, for example, can often narrow the search if other details associated with them work properly or not. If multiple parts or targets fail at the same time, the fuse or ground connection may be faulty, as multiple circuits are often driven through the same fuse and ground connections.
Electrical failures are often caused by small things, such as poor contact or corroded connections, or a fuse. Before troubleshooting, always visually inspect the condition of the fuse, wires, and connections in the circuit.
If you are going to use the appropriate tools for testing, use the diagrams so that you can navigate to the right places to determine the malfunction.
Basic tools needed for electrical troubleshooting - tester or voltmeter (a 12 volt light bulb can also be used, with a set of load resistors), a battery and a set of load resistors, a jumper, preferably with a reverse current relay switched on, which is used to bypass electrical parts.
The voltage in the circuit indicates that it is working properly. Connect one tester lead in the circuit to either the negative pole of the battery, or a good ground. Connect the other wire to a point on the circuit under test, preferably as close to the battery or fuse as possible. If the light is on, then the voltage reaches this point, which means that part of the circuit between the connector and the battery is good. Continue checking the chains in the same way. When you get to the point where there is no voltage, the fault lies between that point and the last good point, most faults are due to poor contact.
Note: Be aware that some circuits are only energized when the ignition key is in the On or Start position.
The way to detect a short in the circuit is to remove the fuse and insert a test light or voltmeter into the fuse clips. There should be no voltage in the circuit. Move the test harness from side to side, watching for voltage. If the light comes on, then there is a short circuit to ground or the insulation is damaged. You can also check other targets, including the switches themselves.
The ground test also allows you to find many faults. Disconnect the battery and connect one lead of the bulb probe to a well-known ground. Insert the other wire into the ground to be tested. If the light is on, the ground is good.
Conductivity indicates whether a circuit or individual part conducts electricity properly. Disconnect the battery and connect one probe lead to one end of the circuit and the other to the other. If the light turns on, there is a contact, which means the target is passing electricity properly. Switches are tested in the same way.
Remember that all electrical circuits are made up of electricity flowing from the battery through wires, switches, relays, etc. to an electrical part (incandescent lamp, engine, etc.). Next, the current flows to the body (grounding), where it gets back into the battery. Any electrical failure is an interruption in the flow of electricity from and to the battery. Simply put, malfunctions in the electrical system occur due to the lack of contact or the presence of excess.