A FAW Volkswagen Jetta car, when the vehicle is in use, opens the air conditioner, and the radiator fan runs at high speed. After the air conditioner is turned off, the fan runs at high speed. After the ignition is switched off, the fan is still operating at high speed, the battery connection is removed and the radiator fan stops. When the battery is connected again, the fan doesn't work, but when the engine is started and the air conditioner is turned on, the radiator fan runs at high speed. Turn off the engine and air conditioning, and the fans are still running at high speed.