Contents: Checking voltage ↧ Short circuit detection ↧ Checking contact with the "mass" ↧ Checking the continuity of the… ↧ Gap detection (open circuit) ↧
Before you begin repairing any electrical circuit, first review the circuit diagram to clearly understand what components make up the circuit. For example, you can often narrow down the scope of your troubleshooting by first determining that some components in a given circuit are working properly. If several devices or circuits fail simultaneously, it is possible that the source of the malfunction is a blown fuse or poor contact with the ground, since several circuits are often served through one fuse or ground wire.
Faults in electrical circuits usually occur for relatively simple reasons, such as loose or corroded contacts, a blown fuse, or a faulty relay. Therefore, before starting repairs on a failed circuit, perform a visual inspection of the condition of all fuses, wires and contacts in that circuit.
If you plan to use measuring instruments, plan in advance by studying the diagrams where they should be connected in order to accurately locate the fault.
The main devices needed to troubleshoot electrical circuits are a tester or voltmeter (you can also use a 12-volt test light with a set of wires).
Checking voltage
If the circuit is not working properly, check the voltage in it. Connect one of the tester leads to the negative terminal of the battery or to the "ground". Touch the other lead of the tester to any electrical contact of the circuit being tested (preferably closest to the battery) or to the fuse. If the tester lamp lights up, this means that there is voltage in the circuit and the section of the circuit between this electrical contact and the battery is OK. Check the remaining sections of this circuit in a similar manner. When you reach a point where there is no voltage, it means the fault is between that point and the last point where there was voltage. In most cases, the fault comes down to a loose contact.
Note: Be aware that some circuits are only energized when the ignition key is in the "Accessory" or "Run" position.
Short circuit detection
One method of detecting a short circuit in a circuit is to remove the fuse and connect a test lamp or voltmeter to the terminals in its place. There should be no voltage in the circuit. Move the wire harness from side to side while watching the test lamp. If the lamp lights up, it means there is a short circuit to ground somewhere nearby, perhaps where the insulation has worn through. Any element of the circuit, including the switch, can be subjected to a similar test.
Checking contact with the "mass"
The ground contact check is performed to ensure that a particular circuit element has a good ground connection. After disconnecting the battery, connect one of the test lamp terminals with its own power source (this device is called a continuity tester) to a contact that is known to be connected to ground. Connect the other end of the wire to the wire you want to test. If the lamp lights up, then the contact is good.
Checking the continuity of the circuit
A circuit continuity test is performed to determine if there are any breaks in a given circuit (if under normal conditions it passes current). Turning off the chain (there should be no tension in it), you can use a continuity tester with its own power source to check it. Connect the test leads of the tester to both ends of the circuit, and if the lamp lights, then the circuit is conducting. If the lamp does not light, then there is a break somewhere in the circuit. A switch can be tested in a similar manner by connecting a continuity tester to its contacts. When you turn on the switch, the lamp should light.
Gap detection (open circuit)
When testing electrical equipment to determine if there is an open circuit, visual detection is often difficult because oxidized areas or loose contacts may be hidden in electrical connectors. Sometimes, to restore contact, it is enough to move the electrical connector on the sensor or the wiring harness. This should be kept in mind when searching for open circuits. Oxidized or loose contacts can also be the cause of intermittent circuit breaks.
Troubleshooting electrical equipment becomes relatively simple when you consider that the current in all electrical circuits flows primarily from the battery through wires through switches, relays and fuses to all electrical devices (lamps, electric motors, etc.) to ground, from where it returns back to the battery. Therefore, any fault in an electrical circuit is essentially nothing more than an interruption of the electric current coming from the battery and returning to it.
(The source of the article is available on the website CHEVYMAN.ru)