A Honda three car flying car with a mileage of about 160 thousand km in 2006. After parking for one night in the parking lot, the second day appeared the phenomenon that the whole vehicle was without electricity and the engine could not start. Fault analysis: analysis of the possible causes of the car's whole car without electricity, such as bad battery, fuse fuse, poor contact of battery pole, short circuit or circuit breaker. Because the vehicle is a rescue vehicle, the first judgement may be battery failure. Directly connected with the standby battery, it is found that the whole vehicle is still without electricity. Use the multimeter to check the battery voltage, normal. Check the connection lines on the positive and negative poles of the battery. They are firmly connected. Using the test lamp to check the power supply of fuse in fuse box, it is found that the fuse voltage supplied to the electronic fan is insufficient, the test lamp is dark, and the other fuse is normal. When the test lamp inspects the battery negative electrode to the body, it is found that the test lamp can light up. Is there a short circuit in the electronic fan control circuit? Since the ignition switch is connected, the instrument and the related electric equipment are not electric, so the driver's side panel is removed and the ignition switch is found. It is found that there is a voltage between the power line and the bypass, but it can not light the test lamp. The headlights can be controlled by the switch when the car does not connect the ignition switch, but there is no power supply for headlights. Suspicion of poor contact for common power or feeder lines. It was found that there was an accident in the left front of the car. There was a trace of spray paint on the battery negative electrode and the body connection. It was found that the connection had been rusted and the contact was bad. Troubleshooting: handle the connection point between the battery negative electrode and the body.