The low-pressure pipe of Swift air conditioner is very cold, so the wind blown out is not so cold.

The compressor and expansion valve have been changed, and the condenser is new. To solve the problem, the compressor and expansion valve have been changed, and the condenser is new. Solve it, and it's urgent. First of all, let's understand the principle of air conditioning refrigeration: the low-pressure steam of refrigerant in the refrigeration system is sucked by the compressor and compressed into high-pressure steam and then discharged into the condenser, and the indoor air is continuously circulated to reduce the temperature. Simply put, it is the same as the familiar principle of household air conditioning refrigeration. They are all based on the principle that the rapid expansion of the instantaneous volume released by R 12 or R 134a will absorb a lot of heat energy for refrigeration (at present, R 134a is mostly used in automobile air conditioners). Automobile air conditioning is divided into four parts, namely condenser, evaporator, compressor and throttle expansion valve. Understand the principle of air conditioning refrigeration and some main components, and then analyze the common fault points of air conditioning refrigeration at idle speed, but when driving. 1. The refrigerant in the air-conditioning system completely leaks, resulting in no refrigerant, so the air conditioner does not cool. Solution: You can check some components in the air conditioning system, such as pipelines, air conditioning pumps, condensers, evaporation boxes, etc. Damage and cause refrigerant leakage. There is also an inspection method, which can add fluorescent agent at the same time as refrigerant. After the vehicle has been used for one week, check the air conditioning system with a special fluorescent lamp. If there is a leak, it will light up, indicating that this part is damaged. 2. The air-conditioning pump is damaged internally, such as the piston ring and clutch sucker inside the air-conditioning pump. As a result, the air conditioning pump cannot work and the refrigeration effect cannot be started. Generally, abnormal sound will appear when the air conditioning pump is damaged. Solution: Check the air conditioning pump. If it is damaged, it needs to be replaced. 3. The condenser radiator in the air conditioning system is too dirty, which leads to the high pressure and temperature of the air conditioning system. In order to protect the air conditioning system, the air conditioning water pump stops working, so the air conditioner does not cool. When driving, the air conditioning system can be cooled by the vehicle speed, so the air conditioning system will be cooled when the vehicle is driving. Solution: You can use a high-pressure water gun to clean the radiator of the lower condenser. After cleaning, blow dry with a high-pressure air gun. Understand the wage principle of air conditioning heating. According to the types of heat sources, automobile heating systems are mainly divided into two types: one is to use engine coolant as the heat source (currently used by most vehicles), and the other is to use fuel as the heat source (used by a few middle and high-class vehicles). When the engine coolant temperature is high, the coolant flows through the heat exchanger in the heating system (generally referred to as the small heater tank), and the air sent by the blower exchanges heat with the engine coolant. After being heated, the air is sent into the car by the blower through various air outlets. The heat source we know is the principle of heating by using the heat of coolant, so we should first check whether the coolant is enough. If there is a lack of coolant, the heating effect of the air conditioner will be poor. You also need to check whether the cooling fan is working properly. If the cooling fan rotates frequently, the water temperature cannot rise, and the heating effect of the air conditioner will become worse. The blockage or leakage of the warm air tank will also lead to poor heating effect or even no heating. The above points are the most common fault points of poor air conditioning heating. Therefore, it is necessary to change the coolant regularly. If the coolant is not replaced for a long time, it will lead to the deterioration of the coolant, the cooling effect will be reduced, the heater box will be blocked, and the heating effect of the air conditioner will be poor. The replacement cycle of coolant is generally about 2 years and 6 kilometers. In fact, there are many reasons for the poor refrigeration effect of automobile air conditioning. The first is the choice of air conditioning cycle mode. When the circulation mode of air conditioner is switched to external circulation, the refrigeration effect of air conditioner is not as good as that of internal circulation, because when air conditioner sends out cold air or warm air, it will bring in the wind outside the car, which is beneficial to the circulation of air inside the car, but the effect of air conditioner is affected. In addition, the evaporator of the air conditioner is dirty. When the evaporator of the air conditioner is densely covered with dust, the condensed water generated on the evaporator will gather on the dust, which will affect the refrigeration effect of the air conditioner. At this time, it is necessary to clean the evaporator of the air conditioner. Finally, the compressor lacks refrigerant, that is, freon. This requires checking the pipeline pressure of the air conditioner. If the pipeline pressure of the air conditioner is abnormal, it is necessary to check where the whole pipeline of the air conditioner is leaking. Because the whole air conditioning pipeline of the vehicle is completely closed, there is no shortage of refrigerant under normal circumstances. As long as there is a lack of refrigerant, there must be a leak. You must check whether there is any leakage, and then replenish the refrigerant, otherwise it will leak if it is added blindly for a long time. If the leakage is large, the cooling effect will start to be poor. If the leakage is small, it may last for a year. In addition, there will be frequent refrigerant leakage. Adding refrigerant will eventually lead to the leakage of lubricating oil in the compressor with refrigerant. When the lubricating oil in the compressor leaks completely, the motor of the compressor will eventually burn out. From what you described, if the refrigerant/condenser of the car air conditioner is missing or leaking. Because the fan of your car's air conditioner is still working effectively, after the refrigerant leaks, the compressor has no exhaust and the condenser has no temperature, resulting in no refrigerant evaporation in the evaporator inside the car, so there is no cold air coming out. I suggest you first try to adjust the gear of the air outlet of the air conditioner to see if the air volume has decreased, and then go to the 4S shop or repair shop to check the pressure of the air conditioning refrigeration system. If the pressure is low, it must be the cause of refrigerant leakage. Just make up in time. There are many reasons for the high pressure on the low pressure side, such as excessive refrigerant charge, poor condensation effect of condenser, high ambient and indoor temperature (beyond the design working range of subtropical air conditioning), maladjustment of expansion valve, etc. In the process of air conditioning operation, the temperature of low-pressure return pipe is not constant, which is related to the heat dissipation effect of condenser, the temperature in the car and the wind speed of blower. It really takes some experience to judge intuitively by touching. As a coil fin heat exchanger, the evaporator itself will not fail unless it is damaged by external force. However, if the evaporator is dirty or frosted, it will be blocked, so that the hot air in the car can not exchange heat with it, and the wind naturally blown out of the air outlet will not be cold. After the evaporator is blocked, there will be an obvious feature, that is, the wind speed at all levels of the outlet is weaker than before. In addition, the cold and warm adjustment of Swift air conditioning system is not realized by adjusting the opening of the water inlet valve of the small water tank (there is no such water regulating valve at all), but by adjusting the air valve with cold and hot air in the air duct, that is to say, whether the cold and warm adjustment knob is turned to the red section or not, the hot water of the cooling system will circulate in the small water tank in the car. If there is something wrong with the air valve, there will be heat to offset the cold of the evaporator. If the low-pressure return pipe is obviously lower than the normal temperature, it is very cold by hand (even feels like cold hands), indicating that the refrigerant has not completely evaporated in the evaporator, and there is still liquid refrigerant flowing to the back end to continue evaporation (the evaporation point moves backward). Evaporation is a process of absorbing a lot of heat, just like boiling a pot of water and then drying it constantly. The process of water from boiling to drying is called evaporation. The liquid water in the pot evaporates into gas and runs into the air. The evaporator of the air conditioner forces the air in the car to circulate repeatedly through the blower, so that the air exchanges heat with the surface of the evaporator. If the evaporator surface is covered with ice or dirt, it loses the function of heat exchange with air. The refrigerant injected into the evaporator through the expansion valve can't get enough heat and can't completely evaporate from liquid to gas. Under the action of pressure difference, it continues to flow to the back end and continues to absorb heat and evaporate during the flow. The low-pressure air return pipe from the firewall to the compressor is bare aluminum pipe, and the heat absorbed in this section can be evaporated, just like turning it into a second evaporator, so it will be very cold and even frozen. The evaporation temperature of the air conditioner is designed at zero degrees Celsius, so it will not freeze or frost under normal circumstances. But if there is too little refrigerant, the evaporation pressure will be lower than normal, so the evaporation temperature will also be lower. Once it drops below zero, its surface will freeze or frost. Evaporation temperature is inseparable from evaporation pressure. Under the standard atmospheric pressure of 1 in the plain, the evaporation temperature of water is 100 degrees Celsius, but why does it boil and evaporate at 80 degrees on the plateau? The reason is that the air pressure in the environment has become lower. I don't know. I read that article last year, but I forgot the details. It's just a sensor. When it detects that the evaporation box is going to freeze, it stops the compressor or something. Anyway, it just doesn't let the evaporation box continue to cool down, which leads to freezing. @20 19