Finding the source of a fault in an electrical system (Mazda Capella GE)

Finding the source of the malfunction

Insert a thin probe into the back of the connector until it touches the desired terminal – connect the voltmeter to the probe.

A typical electrical circuit consists of an electrical component, switches, relays, motors, fuses, fuse links or circuit breakers within that component, and wires and connectors that connect that component to the battery and the vehicle body. To assist you in locating the source of electrical system malfunctions, vehicle electrical system diagrams are provided at the end of this manual.

Before attempting to determine the source of a fault, first study the relevant electrical circuit diagram to gain an understanding of the components installed in that circuit. The range of possible sources of failure can be narrowed down by checking the functioning of other elements included in the given circuit. If several components or circuits fail at the same time, the problem is obviously in the fuse common to these circuits or components, or in the contact with the vehicle body.



Electrical problems are usually caused by simple issues such as loose or corroded connectors, poor contact with the vehicle body, a blown fuse, a melted fuse link, or a faulty relay. Visually inspect the condition of all fuses, wires, and connectors in the faulty circuit before proceeding to check the remaining components.

If you are going to use test instruments, use the electrical circuit diagram to determine which terminals need to be tested to locate the source of the fault.

The main tools needed to locate the source of the fault are a circuit tester or a voltmeter (a 12-volt light bulb and a pair of wires with probes on the ends can also be used to perform some tests); ohmmeter (for measuring resistance and checking circuits for integrity); battery and a set of wires with probes; a jumper wire, preferably with a circuit breaker or fuse, which is used to bypass the wires or elements being tested.

A voltage test in the circuit should be performed if the system is not functioning properly. Connect one probe of the circuit tester to the negative battery terminal or a properly grounded part of the vehicle. Connect the second probe to the terminal in the circuit being tested, preferably the one closest to the battery or fuse. If the light on the tester lights up, there is voltage at that connector, which means the circuit section between the battery and that connector is OK. Continue checking the entire chain in the same manner. When you find a point where there is no voltage, it means the fault is between that point and the last place where there was voltage. In most cases, the cause of the malfunction is poor wiring connection.

Caution: Remember that some circuits only receive voltage when the ignition key is turned to the on or start position.

In order to find the location of a short circuit in the system, it is necessary to remove the fuse and connect a test lamp or voltmeter in place of the fuse. There should be no voltage in the circuit. Move the wires from side to side and watch the test light. If the light comes on, it means that somewhere in this area there is a short circuit to the vehicle's ground, most likely in a place where the insulation has worn off the wires. The same test can be performed on other circuit components, including the ignition switch.

A grounding test should be carried out to check the reliability of the grounding of an electrical equipment element. Disconnect the battery and connect the probe of a test light with its own power source, such as a continuity tester, to one end of the circuit and the other probe to the other end of the circuit. If the light comes on, it means the grounding is good. If the light bulb does not light, the grounding is poor.

A circuit continuity test is performed to check whether a circuit, section of a circuit, or element of a circuit conducts current well. Disconnect the battery and connect the probe of a test light with its own power source, such as a continuity tester, to one end of the circuit and the other probe to the other end of the circuit. If the light comes on, it means that the circuit is not broken and is conducting electricity. Switches can be tested in the same way.



Remember that in a car's electrical circuit, current flows from the battery, through wires, switches, relays, etc. to electrical components (light bulbs, motors, etc.). From them, the current goes to the car body (ground), through which it returns to the battery. Any electrical fault is caused by an interruption in the flow of current from and to the battery.

Checking voltage

Lack of voltage on an electrical component is most often caused by a poor connection. Check the continuity of the circuit between the battery and the electrical component using a voltmeter.

Finding a short circuit

To check for a short circuit, remove the fuse and connect a test light or voltmeter to the fuse connection terminals. There shouldn't be any tension. Move the wire being tested from side to side. If the light comes on, it means there is a short circuit. The same test can be carried out on any piece of electrical equipment, even a switch.

(The article is copied from the resource Mazbook.ru)

Checking the reliability of grounding

Disconnect the battery and connect one wire of the test lamp with the power source to the ground, and the other to the ground wire of the element being tested. If the light comes on, the grounding is OK.

Checking the integrity of the circuit

To check the continuity of the circuit, use a test lamp with a power source. If the light comes on, the circuit is OK.

Finding a break in the chain

If current does not flow through a circuit, it is most often caused by a loose or corroded connection. Shake the suspect wire or connector - this may restore conductivity.