Why Does the Low-Pressure Pipe of a Car's Air Conditioner Freeze?
3 Answers
The reason for the low-pressure pipe of a car's air conditioner freezing is due to a malfunctioning expansion valve or a failed evaporator temperature sensor. Below are the related explanations for the faults: 1. Malfunctioning Expansion Valve: The low-pressure pipe of a car's air conditioner freezing is most likely caused by a malfunctioning 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 expansion valve's opening cannot be adjusted lower). This issue is generally irreparable, and a new expansion valve needs to be replaced. 2. Failed Evaporator Temperature Sensor: It may be due to a failed evaporator temperature sensor. This component is designed to detect the surface temperature of the evaporator and transmit the data to the automatic air conditioning control unit. When the temperature drops below 2°C, the air conditioner will stop operating to prevent frost or ice formation. If 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 replaced.
There are generally several common reasons for the icing of the low-pressure pipe in a car's air conditioning system. I've found that both overcharging and undercharging of refrigerant can cause this issue. When there's too much refrigerant, the system pressure becomes too high, causing the expansion valve to malfunction and leading to a sudden drop in temperature in the low-pressure pipe, resulting in frost. Insufficient refrigerant, on the other hand, leads to poor airflow circulation, which also causes icing. A faulty expansion valve is another major cause; a stuck or worn valve core can allow refrigerant to flow directly through the low-pressure pipe, causing uncontrolled temperature drops and freezing moisture. The presence of air or moisture impurities in the system can also form ice blockages in the pipes when exposed to low temperatures. Regular checks of the refrigerant level are crucial—it's recommended to have a professional inspection annually to avoid the risks of DIY refills. Replacing the dryer to keep the system dry can also effectively prevent this issue. Don't delay until it affects driving safety.
I personally experienced the issue of the low-pressure line freezing in my own car. It was during summer when the AC suddenly stopped blowing cold air, and hot air came out of the vents instead. When I got out and checked, the pipe was covered in white frost. The mechanic explained that a refrigerant leak caused pressure imbalance, leading to the pipe temperature dropping too low and freezing. I had neglected AC maintenance, and the cabin air filter hadn’t been changed for years—it was completely clogged, worsening the airflow issue. The fix was simple: replacing the filter and topping up the refrigerant. This reminded me not to just use the AC without maintenance, or else the unbearable heat on the road could easily lead to trouble. I recommend fellow drivers regularly check and clean the cabin air filter and vents—it saves money, hassle, and reduces breakdowns.
