Contents: Finding an open circuit 🠛 Finding the location of a short…🠛 Finding a short circuit to ground 🠛
An electrical circuit consists of electrical components, switches, relays, motors, fuses, reverse current relays, and wiring. To find the exact fault in an electrical circuit, the electrical connection diagrams are given at the end of this manual.
Before diagnosing an electrical circuit, first study the electrical wiring diagram. If several components fail at the same time, the problem may be related to a fuse or ground.
Electrical faults are usually caused by simple issues such as corroded connections, a faulty ground connection, a blown fuse or a faulty relay (refer to Section General description of fuses and relays). Visually inspect the condition of all fuses, wires, and connections in the application circuit before testing components. Use the wiring diagrams to accurately locate the fault.
The basic tools required to troubleshoot an electrical fault are a circuit tester or voltmeter; stroboscope; ohmmeter; battery and a set of load resistors. Before troubleshooting the instrumentation, use the wiring diagram to determine where to make connections.
To locate a break in the wiring, wiggle the wiring. This testing method can be used in conjunction with other tests described in the following subsections.
Besides broken connections, the two main types of electrical circuit failure are open circuits and short circuits.
Circuit damage caused by breakage prevents current from flowing to the elements.
A short circuit is usually caused by damage to the insulation of the wiring, which allows the power wire to touch either another wire or a grounded part of the body. The short circuit causes the fuse to blow.
Finding an open circuit
1. To test for an open circuit, connect one wire with a circuit tester or voltmeter to the negative battery terminal.
2. Connect the other wiring of the circuit being tested, preferably close to the battery or fuse.
Turn on the ignition.
3. If voltage is present, the circuit between the connector and the battery is good.
4. Continue checking the rest of the chain in the same manner.
5. When a point is found where no voltage is present, the fault is between that point and the previous voltage point tested. Most faults can be caused by broken, corroded or loose connections.
Finding the location of a short circuit
1. Before you begin searching for a short circuit, disconnect the electrical equipment from the circuit.
2. Remove the appropriate fuse from the circuit and connect a tester or voltmeter to the fuse connection.
3. Turn on the ignition.
4. If voltage is present, there is a short circuit in the circuit.
5. If there is no voltage, this indicates internal damage to the electrical equipment.
Finding a short circuit to ground
This note was copied from the resource RenaultBook
1. The negative terminal of the battery is connected to the car body. This means that the engine, transmission and body form part of the circuit. Open or corroded elements can cause a range of short circuits in the electrical circuit, up to and including complete failure of the circuit.
2. Check if the component is properly grounded. Connect the battery cable terminal with an ohmmeter to a known good ground point. Connect the other wiring to the ground being tested. The ohmmeter reading should be zero; if not, check the connection as follows.
3. If the grounding is faulty, clean the ground contact surfaces to bare metal and tighten the connections securely when reassembling; if installing a wire clamp, use serrated washers to ensure a good connection. Lubricate the connection with Vaseline or other lubricant.