A 2007 F3, at 8 o'clock in the evening, the owner called to say that ABS lights were on, the handbrake lights were on, and the call request was supported. After inquiring about the power and brake system has no obvious influence, tell the owner to drive slowly to the repair shop. 20min received a call from the owner again, saying that the car could not go. Fortunately, it was only 2KIN distance from the repair shop. The car was towed back to the factory. The owner told me that in fact, the car's headlights were no longer bright, and it had gone 3kin many times. I asked the owner whether the power was affected when the headlights were not lit. Trying to strike a fire, apparently the battery was out of power, so he asked the owner of the car. At that time, he didn't notice whether the charging lamp of the battery was on. After the night to drag the car back to the factory, with a fire method, the car is still unable to take the car, KT600 diagnostic instrument test, no fault code. At this time the sky was black, the car was put in second days, to another technician to deal with the fault. At that time, I told the technician that it should be short of a circuit short circuit (the discharge was too large to cause battery failure) rather than the general generator failure. The technician took the car keys, hit the fire, the car was "clicking, clicking" (starting machine speed slower) two after the car, when the other car called the other car on the outside to rescue, so the F3 car went to the rescue. Before long, the technician on duty replied that the car could not go back halfway and asked for another car to reinforce. After returning to the factory, the battery was measured without electricity (only 9V). The technician on duty decided that he needed to replace the generator for a generator failure. Replace one of the same type of generator with the same type of generator to catch the fault still! Suspect the new generator has a problem, then put one up, the problem is still not solved! So the generator installed back to the original. When the technician asked me for teaching, I told the car again the possibility of short circuit fault, retest the wire harness from the generator to the dashboard and the safety seat. It was found that there was a plug interface due to bad contact, which caused the current to increase heat, and finally caused the short circuit and burnt. After cleaning the wiring, the fire is normal. The measured power generation capacity of the original vehicle generator is only 12.6V when 2000r / min is generated, and the generating capacity is not enough. So the new generator was replaced, and the trouble was completely eliminated. Fault summary: from this vehicle's malfunction attestation a phenomenon: if the system voltage is low, it often causes many fault lights. After the car is towed back by different technicians and then stop for a period of time, the generator does not generate electricity. The position of the short circuit is not short circuited or short circuit resistance is large after cooling, which gives the technician a kind of illusion, not the problem of short circuit. Therefore, to repair the car or to know more about the process of vehicle failure, it is possible to make the fault diagnosis faster and more accurate.