Contents: Checking voltage ⤓ Short circuit detection ⤓ Grounding check ⤓ Conductivity test ⤓ Search for open circuits ⤓
A typical electrical circuit consists of an electrical component, several switches, actuator relays, fuses, fuses, or circuit breakers associated with the unit, and wires and connectors that connect the component to the battery and chassis. To help solve electrical problems, wiring diagrams are included at the end of the book.
Before you begin troubleshooting a circuit, study the circuit diagram to get a clear picture of the components that make up the circuit. You can usually isolate a faulty component by process of elimination, knowing that the rest of the circuit is working properly. If several components in a circuit or several circuits have failed, the problem may be with a fuse or ground, as it is common for several circuits to share a fuse and ground.
Often the causes of faulty electrical circuits are very simple, it could be a loose or corroded connection, a blown fuse, a melted insert or a bad relay. In a faulty circuit, first inspect the fuses, wires and connectors.
If it is necessary to use control equipment, determine its connection points in advance using electrical diagrams.
The basic tools needed are a tester or voltmeter (a 12V bulb with a set of leads can be used), a continuity tester that includes a bulb, battery and a set of leads, an auxiliary jumper lead, preferably with a built-in circuit breaker and switch that allows you to bypass electrical components. Before attempting to locate a fault with test equipment, determine on the electrical diagram where it is connected.
Checking voltage
Voltage testing is performed when a circuit is not working properly. Attach one lead of the tester to either the negative battery terminal or to ground. Attach the other lead to the terminal of the circuit being tested that is closest to the battery or fuse. If the tester light comes on, there is voltage in the section of the circuit between the battery and the terminal. Continue testing the rest of the circuit in the same way. When you find a point with no voltage, you can be sure that the fault is between that point and the last point that is energized. In many cases, the fault is caused by loose connections.
Note: Be aware that for many applications, voltage is only present when the ignition key is in the Accessory or Run position.
[The text of the article was taken from the website: mitsubishiman]
Short circuit detection
One method of determining a short circuit is to remove the fuse and connect a tester or probe to the fuse terminals. There should be no voltage in the circuit. Move the wiring harness from side to side, watching the lamp. If the lamp lights, then there is a short to ground somewhere in that area, possibly the insulation has worn through. A similar test can be done for any component in the circuit, even a switch.
Grounding check
A ground test is performed to determine if a component is possibly grounded. Disconnect the battery and connect one lead of a self-powered tester (continuity tester) to ground. The other lead of the tester to the wire or ground connector being tested. If the lamp lights up, the ground is OK and vice versa.
Conductivity test
Continuity testing is performed to determine if there is an open circuit. With the circuit off (no voltage in the circuit) a continuity tester can be used to test. Connect the tester leads to both ends of the circuit (or to the "power" end of the circuit and ground), if the lamp lights, the circuit is conducting electricity. If the lamp does not light, there is an open circuit. A similar procedure can be used to test a switch, a continuity tester is connected to the input and output of the switch. With the switch on, the lamp should light.
Search for open circuits
This diagnostic is always quite difficult to perform visually, since oxidation and displacement of the terminals are usually hidden by the connectors. Just shake the connector on the sensor or wiring harness, the circuit will close. Interruption problems can also be caused by oxidation or loose connections.
Troubleshooting is fairly simple if you keep in mind that electrical current flows to all electrical components (lamps, actuators, etc.) from the battery through wires, switches, relays, fuses, and fuse links and to ground, where it returns to the battery. Most electrical circuit problems are due to interruptions in the circuit.