Note: Please refer to the precautions given in Chapter 1 of this Section.
The electrical circuit consists of electrical components, switches, relays, motors, fuses, reverse current relays, electrical wiring. To find exactly a fault in an electrical circuit, the wiring diagrams are given in end of this section.
Before diagnosing an electrical circuit, first study the wiring diagram. If several elements fail at the same time, the problem may be with a fuse or ground.
Electrical faults are usually caused by simple causes such as corroded connections, a faulty ground, a blown fuse or a defective relay (be guided Chapter 3). Visually inspect the condition of all fuses, wires, and connections in the applied circuit before testing components. Use wiring diagrams to pinpoint the exact location of the problem.
Basic tools required for electrical troubleshooting:
- a) circuit tester or voltmeter:
- b) stroboscope;
- c) ohmmeter;
- d) battery
- e) set of load resistors.
Before troubleshooting instrumentation, use the wiring diagram to determine where to make connections.
Move the wiring to locate the break in the wiring. This test method can be used in conjunction with other tests described in the following subchapters.
Apart from broken connections, the two main types of electrical circuit damage are open circuit or short circuit.
Circuit damage caused by a break prevents current from flowing to the elements.
A short circuit is usually caused by damage to the wiring insulation that allows the supply wire to touch either another wire or a grounded body component. A short circuit will blow the fuse.
Finding an open circuit
To test the circuit, connect one wire with a circuit tester or voltmeter to the negative battery post.
Connect other wiring of the circuit under test, preferably close to the battery or fuse.
Turn on the ignition.
If voltage is present, the circuit between the connector and the battery is good.
Continue checking the rest of the chain in the same way.
When a no-voltage point is found, the fault lies between that point and the previous test point with voltage. Most failures can be caused by broken, corroded or loose connections.
Search for a short circuit
Before starting the search for a short circuit, disconnect the electrical equipment of the uncoupler.
Remove the appropriate fuse from the circuit and connect a tester or voltmeter to the fuse connection.
Turn on the ignition.
If voltage is present, there is a short circuit in the circuit.
If there is no voltage, this indicates internal damage to the electrical equipment.
Finding a short to ground
The negative terminal of the battery is connected to the car body. This means that the engine, transmission and body form part of the chain. Open or corroded components can cause a range of short circuits in an electrical circuit, up to and including complete failure of the circuit.
Check if the component is well grounded. Connect the battery connector and wiring with an ohmmeter to a known good ground point. Connect other wiring to the earth to be tested. The ohmmeter reading should be zero; if not, check the connection as follows.
If the grounding is faulty, clean to bare metal the components of the ground contact surfaces, when assembling, securely clamp the connectors; if a wire clamp is installed, use serrated spacers between clamp and body to ensure a clean and secure connection.
When the connection is made, lubricate it with Vaseline or other lubricant.
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