What Causes the Low-Pressure Pipe of a Car's Air Conditioning to Freeze?
2 Answers
The reasons for the low-pressure pipe of a car's air conditioning freezing include expansion valve failure and evaporator temperature sensor malfunction. The details are as follows: Expansion Valve Failure: The expansion valve has a fault issue, making it unable to sense the real-time temperature of the low-pressure pipe. If the temperature is too low, the low-pressure pipe will definitely freeze (the opening of the expansion valve cannot be adjusted lower). In most cases, this situation cannot be repaired, and a new expansion valve needs to be replaced. Evaporator Temperature Sensor Malfunction: The evaporator temperature sensor is used 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 degrees Celsius, the air conditioning will stop operating, leading to frost or ice formation. Therefore, when the evaporator temperature sensor fails, it naturally cannot detect the corresponding temperature data, causing the low-pressure pipe of the car's air conditioning to freeze. In this case, a new sensor needs to be replaced.
Frost formation on the low-pressure pipe of a car's air conditioning system is generally caused by insufficient refrigerant or inadequate airflow. When there isn't enough refrigerant, the pressure on the low-pressure side of the system drops too low, causing a rapid temperature decrease that leads to frost or ice buildup. Additionally, if the blower fan malfunctions or the cabin air filter becomes severely clogged with dust, the reduced airflow results in insufficient heat exchange, causing excessively low temperatures around the evaporator that transfer to the low-pressure pipe. I once encountered this issue while repairing a car—the owner complained about poor cooling performance, and upon inspection, the filter was found to be extremely dirty. After cleaning it, the situation improved significantly. Frost on the low-pressure pipe not only reduces cooling efficiency but can also lead to pipe ruptures or compressor damage. Therefore, if you notice frost buildup, don't delay—visit a professional shop to check refrigerant pressure and system sealing to prevent more serious problems. Regular maintenance, including filter replacement every six months or seasonally, can help avoid many such issues.
