Why Does the Car's Low-Pressure Pipe Freeze?
2 Answers
The reasons for frost formation on a car's low-pressure pipe are: normal phenomenon, insufficient refrigerant, and pipe blockage. Below are detailed explanations: Normal Phenomenon: When the air conditioner starts operating, due to lower condensation temperature and pressure, the capillary tube supplies less refrigerant than normal, causing the evaporation pressure to drop accordingly. This leads to frost formation on the low-pressure supply pipe. Typically, frost begins to form when the compressor starts running, and the entire frost melting process completes within 5 minutes, after which the air conditioner operates normally. Insufficient Refrigerant: When the air conditioner lacks refrigerant, frost will form on the low-pressure supply pipe, which is a typical malfunction. Partial Blockage: Blockages often occur at the filter outlet or capillary tube inlet. Due to a local blockage in the system, a throttling effect occurs, causing the pressure after throttling to fall below the normal operating value of the air conditioner, resulting in frost formation on the supply pipe.
I often encounter frozen low-pressure car pipes during repairs, usually indicating an issue with the AC system. The main cause is insufficient refrigerant - if the level is too low, the low-pressure pipe temperature drops below freezing, causing moisture in the air to condense into ice. A faulty expansion valve can also slow refrigerant flow, overcooling the pipe. When the evaporator gets clogged with dirt, blocking airflow and creating uneven cooling, this too can cause pipe freezing. This affects AC performance, reducing airflow and making it feel like the cooling isn't working. It occurs more frequently during prolonged driving in hot weather. If you notice pipe freezing, first turn off the AC and switch to external circulation to melt the ice, then promptly check refrigerant levels and system sealing - don't wait until the compressor fails.
