Detecting a fault in an electrical system (Opel Frontera B)

General description

A typical electrical circuit consists of an electrical component, switches, relays, motors, fuses, circuit breakers, wires, and connectors that connect the electrical component to the battery and the vehicle body.

Before attempting to determine the source of a fault, study the relevant electrical circuit diagram to gain an understanding of the components in that circuit. The number of possible sources of failure can be reduced by checking the operation of other components in the circuit. If several components or circuits fail at the same time, the fuse common to these components or circuits may be faulty, or the connection to the body - "ground" - may be broken.

The causes of the malfunction are loose or oxidized connectors, poor contact with the body, blown fuses or faulty relays. Visually inspect the condition of all fuses, wires and connectors in the failed circuit before proceeding to check the remaining components. Use the electrical schematics to identify the terminals that need to be tested to locate the source of the fault.

The basic tools needed to locate the source of the fault are a tester or voltmeter, a 12V test lamp, an ohmmeter, a battery and a set of wires with probes, a jumper, preferably with a circuit breaker or fuse, which is used to bypass the wires or elements being tested.

To find a loose connection or short circuit point (usually due to a poor or dirty connection, or damaged insulation) the wires can be shaken by hand to see if the circuit breaks when the wire moves. In this way, you can find a point with an unreliable connection or a point where a short circuit occurs. This testing method can be used in conjunction with the other tests described below.



In addition to poor wiring connections, there are two other main types of faults that can occur in an electrical system: an open circuit or a short circuit.

The circuit is opened as a result of a break in the electrical equipment circuit, which interrupts the current, causing the electrical equipment element to switch off. A break in the circuit will cause any electrical equipment to fail to operate, but will not cause the fuse in that circuit to blow.

Short circuit faults are caused by a short somewhere in the circuit, causing the current flowing in the circuit to flow through another circuit, most often to ground. A short circuit is usually caused by a break in the insulation, allowing the supply wire to touch either another wire or a grounded element, such as the body. A short circuit causes the fuse of the corresponding circuit to blow.

Detecting a broken chain

To find an open circuit, connect one of the test lamp probes to the negative terminal of the battery or the vehicle ground.

Connect the second probe to a connection in the circuit being tested, preferably located as close to the battery or fuse as possible.

Apply voltage to the circuit. Remember that some circuits only have voltage when the ignition switch key is turned to a certain position.

If voltage is present (what will the illuminated control lamp or voltmeter readings indicate?), this means that the part of the circuit between the connection and the battery is OK.

Continue checking the rest of the chain in the same manner.



[Text copied from this portal: opelbook]

When a point is reached where there is no voltage, it means that the source of the fault lies between this point and the last point where voltage was present. Most problems are caused by poor connection.

Short circuit detection

To check a circuit for a short circuit, first disconnect the load from the circuit (load - these are the elements of electrical equipment that consume electricity, such as lamps, motors, heating elements, etc.).

Remove the fuse for the appropriate circuit and connect a test lamp or voltmeter to the fuse connection terminals.

Turn on the power to the circuits, remembering that some electrical circuits are only turned on when the key in the ignition switch is turned to a certain position.

If there is voltage in the circuit (what does the control lamp or voltmeter reading indicate), means that there is a short circuit in the circuit.

If there is no voltage during the test, but the fuse still blows when the same load is connected, the load element has failed.

Checking the reliability of grounding

The negative terminal of the battery is connected to the "ground" - the body, engine or gearbox. A poor or oxidized fastening may result in component failure or malfunction. Keep in mind that many vehicles use "ground" wires between certain components, such as the engine/transmission, and the body, where there is no direct metal-to-metal contact due to soft rubber mounts or paint.

To check the reliability of the element grounding, it is necessary to disconnect the battery and connect one of the ohmmeter leads to a reliably grounded element. Connect the other lead to the wire or connection to the body that needs to be tested. The resistance shown by the ohmmeter should be zero, if not, check the connection as follows.



If there is any doubt about the reliability of the contact with the "ground", disassemble the connection, remove any dirt and clean the contacts. When reassembling, tighten the connector fastening by applying a layer of technical petroleum jelly or silicone grease to prevent corrosion.

Warnings! Warnings specific to vehicles equipped with the Supplemental Restraint System (SRS).

• Improper maintenance or repair of any component of the SRS system (as well as the SRS related component) may result in injury or death to service personnel (as a result of unauthorized deployment of the airbag), as well as the driver and front passenger (as a result of the SRS system not working properly after unqualified maintenance or repair).
• Maintenance or repair of any component of the SRSv system(or a component associated with it) must be performed only by an authorized dealer.