What Causes the Low-Pressure Pipe of a Car's Air Conditioning to Freeze?
2 Answers
Reasons for the low-pressure pipe of a car's air conditioning freezing: 1. Faulty expansion valve: The low-pressure pipe of a car's air conditioning may freeze largely due to a faulty expansion valve, which fails to sense the real-time temperature of the low-pressure pipe. If the temperature is too low, the low-pressure pipe will inevitably freeze (the opening of the expansion valve cannot be adjusted lower). However, this issue is generally irreparable and requires replacing the expansion valve with a new one. 2. Failed evaporator temperature sensor: It could also be due to a failed evaporator temperature sensor. This component is designed to detect the surface temperature of the evaporator and then input the data to the automatic air conditioning control unit. When the temperature drops below 2°C, the air conditioning will stop operating to prevent frost or ice formation. Therefore, when the evaporator temperature sensor fails, it naturally cannot detect the corresponding temperature data, leading to the low-pressure pipe freezing. In this case, a new sensor needs to be installed.
I've been driving for nearly twenty years and have seen many cases of low-pressure AC lines freezing up. The most common cause is insufficient refrigerant, where the system pressure drops too low, causing the evaporator surface temperature to decrease too rapidly and moisture in the air to freeze directly on it. Another possibility is a faulty temperature control sensor, where the compressor keeps running non-stop without shutting off, allowing low temperatures to accumulate continuously. Expansion valve blockage or desiccant failure may also restrict refrigerant flow and exacerbate cooling. Once on the highway, my AC suddenly stopped cooling, and upon inspection, I found the line frozen solid. I immediately turned off the AC, waited about ten minutes for the ice to melt, and then continued driving. I recommend drivers regularly check refrigerant levels, avoid blasting the AC in cold mode when the engine is overheating, and pay extra attention to the cabin air filter during maintenance to prevent such issues and ensure driving safety. After all, freezing can reduce AC efficiency and even damage compressor components.
