Repair Methods of Automobile Circuit Faults

Common circuit faults

Common faults in automotive circuits include open circuit (broken circuit), short circuit, grounding, etc.

1) Circuit breakage is generally caused by wire breakage, loose wire connection or poor contact.

2) Short circuit The causes of short circuit are: the insulation of the wires is damaged and they contact each other to cause a short circuit; the external wiring screws of switches, junction boxes, lamp holders, etc. are loose, causing the wire ends to touch each other; carelessness during wiring causes the two wire ends to touch each other; the wire ends touch metal parts.

3) Reason for grounding: the live wire directly touches the metal body.

2. Ideas for circuit maintenance

Before repairing an automobile circuit, you must read the instruction manual carefully, identify the circuit, understand its structure, and use appropriate tools to achieve twice the result with half the effort.

When a car circuit fails, it is generally necessary to first understand the symptoms of the fault and the accompanying phenomena, identify the local circuit where the fault is located, and then inspect the local circuit to find out the location of the fault and eliminate it.

A normal car circuit must be:

1) The ignition circuit is able to produce a timing spark of sufficient energy.

2) The power circuit charges stably and can meet the needs of electrical equipment in various states.

3) The starter starts powerfully and separates completely.

4) The lighting and signal systems are fully equipped and perform well.

5) The vehicle's wiring is neat and the connections are fixed and reliable; otherwise, it should be considered that there is a major or minor fault in the circuit.

There are many reasons for circuit failure, such as aging of components, natural wear, improper adjustment, environmental corrosion, mechanical friction, short circuit or open circuit of wires, etc. When a circuit fails, you should be good at using analytical methods to make a preliminary diagnosis of the scope of the failure. Remember not to blindly disassemble, connect or touch without knowing the situation or thinking and analyzing. This will not only delay maintenance, but also cause unnecessary damage. You should be good at discovering abnormal signs and fault characteristics before the failure, and analyze the fault in combination with the whole vehicle circuit to narrow the fault diagnosis to a smaller range as much as possible.

When troubleshooting a fault, you should first check the parts with a higher failure rate and are easy to check, and then check the parts with a lower failure rate and are difficult to check, based on the scope of the fault. Only when the fault of a certain part has been confirmed and it must be opened for repair, can it be disassembled. Try not to disassemble or disassemble as few parts as possible to reduce unnecessary trouble. When troubleshooting a fault, you must also use the correct inspection methods and testing means to increase the speed of troubleshooting and avoid unexpected losses.

When a circuit fails, the car is usually inspected and tested first to determine which component the fault occurs in, and then the external performance and internal parameters of the fault location are tested or inspected to find out the fault point and eliminate it. While repairing the fault, attention should also be paid to the maintenance of the relevant components and circuits to restore them to a better state.

If the electrical equipment is damaged beyond repair, it should be replaced. The specifications and models of the replacement parts should be consistent with the original parts. When replacing the wires, the wire diameter and color should be consistent with the original wires as much as possible. If other colored wires are used instead, they should be distinguished from the adjacent wires to facilitate future maintenance.

Common Fault Troubleshooting Methods for Automobile Circuits

Common faults in automobile circuits include: open circuit, short circuit, damage to electrical equipment, etc. In order to diagnose faults quickly and accurately, several common maintenance methods are introduced below.

1. Intuitive diagnosis

When a car circuit fails, there may be abnormal phenomena such as smoke, sparks, abnormal noise, burning smell, heat, etc. These phenomena can be directly observed, so as to determine the location of the fault.

2. Short circuit method

When a grounding (short circuit) fault occurs in an automobile circuit device, the circuit breaking method can be used to make the judgment. That is, after disconnecting the circuit segment suspected of having a grounding fault, observe whether the grounding fault still exists in the electrical equipment, so as to determine the location and cause of the circuit grounding.

3. Circuit Breaker

If a circuit breaker occurs in the automobile circuit, you can also use the short-circuit method to determine whether there is a circuit breaker fault. That is, use a screwdriver or a wire to short-circuit the circuit suspected of having a circuit breaker fault, observe the changes in the instrument pointer or the working condition of the electrical equipment, and thus determine whether there is a circuit breaker fault in the circuit.

4. Test Light Method

The test light method is to use a car light bulb as a test light to check whether there is a circuit breakers fault.

5. Instrument method

Observe the indications of the ammeter, water temperature gauge, fuel gauge, oil pressure gauge, etc. on the dashboard of the car to determine whether there is any fault in the circuit. For example, when the engine is cold and the ignition switch is turned on, the water temperature gauge does not move at the full scale position, indicating that the water temperature gauge sensor is faulty or the circuit is grounded.

6. Low-voltage grounding fire test method

That is, remove a certain wire end of the electrical equipment and touch it against the metal part (grounding) of the car to generate sparks to judge. This method is relatively simple and is often used by automotive electricians. The grounding test fire method can be divided into direct grounding and indirect grounding. The so-called direct grounding is to directly ground without passing through the load to produce strong sparks. For example, if we want to judge whether there is a fault in a circuit from the ignition coil to the battery, we can remove the wire end connected to the ignition switch on the ignition coil and scrape it on the car body or frame. If there is a strong spark, it means that the circuit is normal; if no spark is generated, it means that there is a circuit break. Indirect grounding is to generate weak sparks through a certain load of the automotive electrical appliance to judge whether the line or load is faulty. For example, ground the connection wire of the traditional ignition system breaker (the loop passes through the primary winding of the ignition coil). If there is a spark, it means that this section of the line is normal; if there is no spark, it means that the circuit is broken. It is particularly worth noting that the fire test method cannot be applied to electronic circuit cars.

7. High-pressure fire test method

Conduct a grounding test on the high-voltage circuit, observe the spark condition, and judge the working condition of the ignition system. The specific method is: remove the high-voltage wire of the ignition coil or spark plug, align it with the spark plug or cylinder head, etc., at a distance of about 5mm, then turn on the starter switch, turn the engine, and observe its sparking condition. If the spark is strong, sky blue, and the sparking sound is loud, it means that the ignition system is basically working normally; otherwise, it means that the ignition system is not working properly.