Basically, there is something wrong with every important part of the air conditioner, and there will be no refrigeration. If you want to find the reason accurately, you must know the current situation of air conditioning, so that you can make an accurate judgment. Too much refrigerant causes insufficient refrigeration, and too much refrigerant is usually caused by too much refrigerant filling during maintenance, because the air conditioning system has requirements for refrigerant ratio. If the proportion is too large, it will affect its heat dissipation, that is, the more heat dissipation, the greater the refrigeration capacity; On the contrary, if the heat dissipation is small, the cooling capacity will be small. Similarly, if too much cooling oil is added during maintenance, the heat dissipation of the refrigeration system will also decrease. Maintenance method: observe from the liquid mirror above the drying tank. If there is no bubble in the mirror when the automobile air conditioner is running, and there is no bubble after the compressor stops running, there must be too much refrigerant. If the amount of pressurized cooling oil is too much, turbid bubbles will appear in the observation window when the air conditioning system works normally. Of course, if there is too much refrigerant, you can slowly release some from the maintenance port on the low pressure side of the air conditioning system. Too little refrigerant leads to insufficient refrigerant, and most of the reasons for insufficient refrigerant are due to micro-leakage of refrigerant in the system. If the refrigerant in the air conditioning system is insufficient, the refrigerant injected into the evaporator from the expansion valve must also be reduced, so when the refrigerant evaporates in the evaporator. The absorbed heat will also be reduced, and the refrigeration capacity will also be reduced. Maintenance method: the lack of refrigerant can also be observed from the observation window above the drying tank. When the air conditioner is in normal operation, if there are continuous and slow bubbles in the observation window, it means that the refrigerant is insufficient. If there is obvious bubble turnover, it means that the refrigerant is seriously insufficient. If the refrigerant is insufficient, it should be added, but it should be noted that if it is added from the low pressure side, it is forbidden to pour the refrigerant bottle, and if it is added from the high pressure side, it is forbidden to start the engine. Insufficient refrigeration capacity caused by excessive impurities and slight blockage in refrigerant and refrigerator oil. If there are too many impurities in refrigerant and refrigerating machine oil in the whole air conditioning system, it will block the filter screen of the filter, which will lead to the decrease of refrigeration capacity and the increase of resistance, and the refrigerant flowing to the expansion valve will also be relatively reduced, resulting in insufficient refrigeration capacity. Therefore, when maintaining air conditioners, it is very important to choose qualified refrigerants, especially those "three days" products. Air conditioning refrigeration system water intake leads to insufficient refrigeration. One of the components in the refrigeration system is the drying tank (bottle), whose main task is to absorb the moisture in the refrigerant and prevent the cooling capacity from decreasing due to too much moisture in the refrigerant. However, when the desiccant in the drying tank is saturated with moisture, water can no longer be filtered out. When the refrigerant passes through the orifice of the expansion valve, due to the decrease of its pressure and temperature, the moisture in the refrigerant will freeze in the orifice, resulting in poor refrigerant circulation, increased resistance or no flow at all. Maintenance method: After stopping for a period of time, the refrigeration system will return to normal after the ice melts. This is an important way to confirm whether there is water in the system. In order to better detect the amount of water in the system, the desiccant used by some cars is blue when there is no water. Once there is too much water, the desiccant will turn red, which can be seen on the side liquid hole on the drying water tank of the car. If there is too much water in the refrigerant, the desiccant or drying tank should be replaced. At the same time, the system should be vacuumized again and injected with new refrigerant again. The air in the system is also one of the reasons for insufficient refrigeration. Once the air enters the air conditioning system, the pressure in the refrigeration pipeline will be too high, and poor refrigerant circulation will also cause insufficient refrigeration. This failure is mainly caused by poor sealing performance of refrigeration system or incomplete vacuum pumping during maintenance. Check whether the compressor drive belt is loose. If the compressor drive belt is loose, the compressor will slip when working, which will reduce the transmission efficiency, thus reducing the compressor speed and the delivery of compressed refrigerant, thus directly reducing the refrigeration capacity of the air conditioning system. Maintenance method: When the engine stops running, move the belt in the middle of the transmission belt by hand, which can rotate 90? ; Preferably, if the rotation angle is too large, it means that the drive belt is loose and should be tightened. If you can't turn it over by hand, it means that the transmission belt is too tight and should be slightly loose. Of course, if the fastening is invalid or the drive belt is damaged due to cracks and aging, a new drive belt should be replaced. The cooling capacity of the condenser will decrease, which will also lead to the cooling capacity of the air conditioner. Because of the different working environment of the automobile, the surface of the condenser installed in front of the automobile engine will be covered with oil or sundries, which will reduce its cooling capacity. In addition, the failure of cooling fan, such as loose drive belt, low fan speed or high fan speed, will lead to the decrease of condenser heat dissipation capacity. Maintenance method: use a soft brush to remove the dirt on the surface of the condenser, and eliminate the fault of the electric fan in time. Other reasons, such as low power supply and voltage, reducing the suction force of the compressor electromechanical clutch or oil pollution between the pressure plate and pulley of the electric clutch, will lead to the phenomenon of "slipping" similar to loose drive belt. If the surface of evaporator is frosted, the speed of blower motor will decrease, which will also cause insufficient cooling capacity. Of course, if the compressor is worn or the valve is improperly closed, it will also cause insufficient cooling capacity of the air conditioner. The failure of air conditioning refrigeration system, such as insufficient refrigeration and poor refrigeration effect, is generally due to the problem of refrigeration seal. Because the refrigerant used in automobiles is very permeable now. Therefore, the sealing requirements of the system are also relatively high, and a slight leakage of the refrigeration working pipeline or valve will cause the failure phenomenon of insufficient refrigeration.