The expansion valve and the orifice pipe are the throttling devices for the refrigerant of the automobile air conditioning system, and have a direct and key role in the cooling effect of the air conditioner. When the high-pressure refrigerant liquid passes through the expansion valve, the flow and pressure entering the evaporator are automatically adjusted according to the evaporation temperature, so that it corresponds to the evaporation temperature.
For the expansion valve and the orifice pipe, it is mainly to check whether the adjustment pressure is normal. When the system is filled with a standard amount of refrigerant, the engine is running at idle speed, and the low pressure pressure should be between 0.15-0.25MPa; otherwise, the expansion valve adjustment is abnormal, and the opening is too large or too small. If the opening of the expansion valve and the orifice is too large, a lot of refrigerants pass through, and the corresponding evaporation pressure and temperature will be high. The temperature of the evaporator and the low-pressure return pipe is not cold, and the refrigeration effect is poor; If it is too small, there will be less refrigerant passing through, the corresponding evaporation pressure and evaporation temperature will be low, the adjusted refrigerant cannot meet the needs of evaporation (heat exchange), and even frost occurs at the outlet of the expansion valve and the evaporator, but refrigeration The effect is still poor.
Dirty plugging of expansion valves or orifices is the most common. When the system is too dirty, the desiccant (silica gel) in the liquid storage drying filter is broken, and when the high-pressure refrigerant liquid flows into the expansion valve or the orifice, the blockage is most likely to be formed in the narrow channel. Cause the liquid supply is not normal, so that the system can not operate normally. When the expansion valve or orifice is dirty and blocked, after disassembly, it can be washed repeatedly with carburetor cleaning agent, and then dried with nitrogen or dried compressed air before reassembly.
Since the evaporating temperature of the air-conditioning refrigeration system is generally above 0 °C, the phenomenon of ice blockage generally does not occur.
The root cause of odors in car air conditioners is usually the evaporator of the refrigeration system. Evaporator is a place for refrigeration and vaporization. It is the vaporization of refrigerant that absorbs a lot of heat to produce the cooling effect of air conditioner. However, as the air temperature decreases, a large number of water droplets will condense on the evaporator. In addition, the evaporator itself also has the effect of air filtration, so there will be impurities in the air in the condensed water.
When the air conditioner is working normally, these impurities will be discharged out of the car with the water, but a small amount will also remain on the evaporator. When the air conditioner stops working, there will also be condensed water that has not been removed on the evaporator. This moisture will combine with dust, viruses and smoke in the air, and mold will grow over time, which will cause the car air conditioner to have a peculiar smell.
