What Causes the Expansion Valve to Freeze?
2 Answers
The reasons for the expansion valve freezing are: severe lack of refrigerant causing frost on the expansion valve; system blockage leading to excessively low flow through the expansion valve, resulting in frost; undersized expansion valve configuration causing frost; operating conditions exceeding standards; and differentiation of non-azeotropic working fluid components. Installation Location: The expansion valve is installed at the inlet of the evaporator and serves as the boundary point between the high and low pressure sections of the automotive air conditioning refrigeration system. Principle: The expansion valve throttles and reduces the pressure of the high-pressure liquid refrigerant from the liquid storage dryer, regulating and controlling the amount of liquid refrigerant entering the evaporator to adapt to changes in the cooling load. It also prevents compressor liquid slugging and abnormal overheating of the vapor at the evaporator outlet.
Expansion valve icing is a common issue in automotive air conditioning systems, and I believe there are several main reasons for this. When the refrigerant expands at the expansion valve, the temperature drops sharply. If the environmental humidity is high, moisture in the air can quickly condense and freeze, especially during hot summer weather. Another common cause is system blockage, where impurities or dust enter the expansion valve, obstructing refrigerant flow and leading to localized low pressure and sudden temperature drops, which trigger icing. Additionally, poor system sealing allowing air or moisture to mix with the refrigerant can exacerbate this phenomenon. I've encountered similar cases before, and car owners should pay attention to regularly checking the air filter and cleaning the system, avoiding excessive use of the air conditioning in dusty environments. Once the expansion valve ices up, the air conditioner may blow hot air or fail to cool, requiring prompt repair to prevent system damage.
