A mileage of about 115 thousand KMR and 2007 Volkswagen Bora 1. 9TDI sedan. The car is equipped with an automatic air conditioning system. The phenomenon of blocking is as follows: after the air conditioning system is opened, the air outlet temperature can not be adjusted. Check the appearance of the air conditioning system, did not find obvious abnormalities. The connection diagnostics is used to detect the vehicle and no fault codes are found. Starting the engine, using the air conditioning refrigeration mode, using the diagnostic instrument to detect the data flow of the air conditioning system. The data of the air conditioning operation state is "0", which indicates the opening of the air conditioning control module, and the electromagnetic clutch of the air conditioning compressor is absorbed. The air conditioning pressure meter is connected to the air conditioning pipeline. The actual measurement results show that the refrigerant pressure on the high and low side is 700kPa, indicating that the air conditioner compressor does not work, and the electromagnetic clutch of the air conditioner compressor has no absorption. In addition, it was found that the cooling fan was not running. Normally, when the air conditioning switch is turned on (the air conditioning mode is activated), the cooling fan will run. According to the working principle of the air conditioning system of the car, the electromagnetic clutch of the radiator fan and the air conditioner compressor is controlled by the air conditioning control module J293. In the previous detection process, the diagnostic apparatus did not detect the failure of the air conditioning control module, the sensor, the actuator and other components, and the operating state of the air conditioner compressor was opened, but why did the air conditioner compressor actually have no work? It seems that the possibility of connection failure is relatively large, so check the whole car power supply line, it turns out that the fuse S180 (30A) on the battery cover burned. Replace the fuse, test the car, the air conditioning compressor electromagnetic clutch suction, the cooling fan running at low speed, but less than 5 min, fuse S180 once again burned, indicating that the circuit has a short circuit fault. Check related wiring harness, no short circuit or breakage. During the process of pulling out and plugging the electrical appliance, it is found that the plug of the heat sink fan is overheated. Through the energizing test of the cooling fan, it is found that the spark is strong, indicating that the fan of the cooling fan is short circuited. Replace the radiator fan assembly, install the relevant parts, test the car, the symptoms disappear, and the maintenance work is over. The air conditioning control module is supplied by the fuse S180. When the fuse S180 is fused, the air conditioning control module can not work normally, causing the air conditioning compressor and the cooling fan not to work. When overhauling, we should pay attention to find out the cause of the symptoms with specific symptoms. The fuse burns slowly because of overheating, which is usually caused by overload or short circuit. The common high-power electrical appliances in the air conditioning system include cooling fans, air conditioning compressors, electromagnetic clutch and blower. These components should be checked during overhaul.