The Beijing BJ2020S cross-country with a mileage of about 85 thousand km. When the vehicle is running, its ammeter always indicates that the 0 bits are not moving. Troubleshooting: (1) failure analysis, failure analysis, possible causes: 1) failure of charging circuit. 2) the ammeter itself has a fault. (2) the troubleshooting method shows that the car does not suffer from battery loss by asking the owner. Therefore, when observing the ammeter when starting the engine, it is found that the ammeter still indicates the 0 position does not move, indicating that the ammeter itself is faulty. The ammeter of the car is electromagnetic, and there is no coil inside, so there is no coil breakage, usually mechanical failure. Therefore, taking out the ammeter check from the combined instrument, it is found that the pointer shaft is out of the bearing position, and the cause of the trouble is found. (3) the fault treatment measures with the pinch clamp bearing screw support, first use small screw screw to spin the small B to screw the bearing screw, and then use small tweezers to clamp the pointer axis, put it in place again; carefully screw into the bearing screw, so that the clearance fit properly, the pendulum will not fall, and will not die, swinging and flexible. Re install the ammeter, charging and discharging instructions are normal, troubleshooting. Fault analysis: if a car equipped with an ammeter is running, if the meter always indicates the "0" position, the generator or voltage regulator usually fails, causing the charging system to be not charged. To verify that the charging system is not charged, it is only necessary to switch on the ignition switch when the engine is out of order to see if the current meter indicates discharge. If the ammeter indicates the discharge when the ignition switch is connected, the ampere indicator is 0 when the engine is running at high speed. It is no doubt that the charging system fails. If the ammeter always indicates 0 bits during the high speed operation of the ignition switch and the engine, it is the fault of the ammeter itself. This case is due to the improper assembly gap of the ammeter, and the impact vibration causes the pointer shaft to die. In the repair and assembly, be sure to note that when the screw is screwed or swirled, the holder should be clamped with the pliers, otherwise, when the screw is whirled with the screw, it is very easy to break the cast aluminum small support and cause the ammeter to be scrapped.