There are many methods for diagnosing automobile circuits and electrical faults. Let's use the following automobile maintenance technology website to summarize them. After reading this, you will know better when to use which diagnostic method. For those who don't understand, think again. 1. Intuitive diagnostic method The intuitive diagnostic method is the first and simplest step in automobile electrical inspection. It uses only the first-hand feel and experience of the inspector to inspect and troubleshoot defects. If a certain part of the car's electrical system fails, abnormal phenomena such as smoke, sparks, abnormal noise, burning smell and high temperature will occur. Through the sensory organs of the human body, you can use the methods of seeing, smelling, listening, cutting and smelling the car's electrical appliances to performr visual inspections and determine the location of the defect. For experienced service personnel, complex faults can be discovered and the repair speed can be significantly improved. For example, when the car is driving and the turn signal switch is on, you suddenly notice that the turn signal and direction indicator light do not turn on. If you touch it with your hand, it means that the flasher relay has become hot. and the flasher relay is burned out. When electrical appliances are functioning properly, they need an appropriate operating temperature. Too high or too low a temperature means a breakdown. For example, when the starter is not moving, if the battery post has poor contact with the wire, it will be hot to the touch. 2. The diagnostic method for testing fire by striking iron is to remove the wires from electrical appliances and try to touchr the metal parts of the car, and to judge the defect based on the intensity of the sparks generated. This method is relatively simple and is a convenient method commonly used by many automotive electronic and electrical repairers. In systems equipped with electronic equipment, this method is generally not allowed and certain instruments and tools must be used in a certain way. Otherwise, the overcurrent generated during the "test fire" will cause unexpected damage to some circuits and components. Diagnostic methods for forging attempts are divided into two types: direct forging and indirect forging. 1) Direct Iron Striking This is a method of judging the condition of the line based on the sparks generated by direct application of iron without putting any load on it. For example, if you think the line from the main light switch to the contactorbrake switch is defective, you can remove the end of the brake switch wire and test it directly with an iron. If there are strong sparks, it means the line is normal. When the spark is weak, it means that one end of the wire in the line is in poor contact or dirty; if there is no spark, it means the line is cut. 2) Indirect forging is a method of evaluating line and load faults based on sparks generated by forging with loads from cars and electrical equipment. For example, if the low voltage (-) side of the ignition coil is poured onto iron, if the spark is weak, it means the circuit is normal. If there is no spark, the circuit is broken. 3. Blockage diagnosis method: The circuit breakage diagnosis method is suitable for faults that occur when a short circuit occurs in the electrical system. For example, if the flashThe door light is always on, this means that there is a ground fault in the circuit of a certain door light switch. In this case, the cut-off method can be used for safety reasons. This is done by pressing or pressing the door light switches one after the other to connect the wiring in a single line. By touch, if there is no spark at any end of the wire, it means the circuit has a ground fault. When the shorted grounded part is found and disconnected, the door light should turn off. 4. Change comparison method refers to the method of replacing electrical appliances suspected of being defective with electrical appliances of the same standard and good performance for comparison to determine the defect. For those that are difficult to diagnose,For faults with many faults (such as ordinators), comparison with replacement parts can be used to determine or refine the extent of the defect. When the high voltage spark is weak and the capacitor is suspected of being defective, a good capacitor can be replaced for a test fire. When the sparks become stronger, it means the original capacitor is damaged, otherwise keep looking. If the engine injector does not inject fuel, it is suspected that the computer is faulty and can be replaced with a good computer. When oil is sprayed, it indicates that the original computer is damaged. Otherwise, keep looking. 5. The test lamp diagnosis method means that a car bulb is used as a test lamp, and the fault state of a certain circuit (disconnection, short circuit, poor contact) is diagnosed by observing whether the test lamp lights up or not or how much it lights up. This method is byparticularly suitable for electrical equipment containing electronic components which do not allow direct short circuits. For example, to test whether an alternator is producing electricity, you can use the pilot light diagnostic method. The method involves removing the wiring from the alternator armature and, with the engine running, connecting one end of the test light to the alternator armature and grounding the other end. If the test light comes on, the alternator is operating normally. On the other hand, we believe that generators do not produce electricity. Additionally, when checking if the car's electrical system is disconnected, you can connect a test light where the disconnection is suspected. If the test light does not illuminate, the circuit is disconnected. Otherwise, the circuit is considered normal. 6. Short circuit diagnosis method: when a low circuithe voltage is suspected to be disconnected, use a wire to short circuit the circuit or electrical appliance, observe the changes in the electrical appliance, then check and determine the fault location. For example, when the brake light does not turn on, you can use a screwdriver to connect the two terminals of the brake light switch to check whether the brake light switch is in good condition. Modern automotive electronic equipment must be careful to use the short circuit method to diagnose faults.
Checking for bypass involves checking whether the engine spark plug is energized.
< p>The specific operation is as follows: disconnect the high voltage wire on a certain cylinder spark plug, and place it in a place 1-2mm away from the surface of the engine body (metal part), start the motor and see if there is any sparking between the high voltage conduction and the metal bodye of the engine.Typically used to check engine instability and shaking.
If there is no current, it means there is no fire in the high voltage wire. Check the ignition coil (for example, replace the ignition coil and try again).
If there is a problem, check the spark plug (spark plug gap and carbon buildup)