What Causes Frosting on the High-Pressure Pipe of a Car's Air Conditioning System?
3 Answers
The reasons for frosting on the high-pressure pipe of a car's air conditioning system are as follows: Blockage: The filter screen is too dirty or the evaporator inside is too dirty, causing obstruction and hindering ventilation. Indoor: The fan speed of the indoor unit is too slow, leading to poor temperature exchange. Fault: There is damage or leakage in the air conditioning pipeline, resulting in a shortage of Freon. Additional information is as follows: Check whether the connecting pipe is tightly connected: If the connecting pipe was extended during installation, check whether there are sand holes at the welding points. If the length of the connecting pipe was reduced during installation, focus on checking whether the flared port you made meets the standard. Blockage of the capillary tube in the machine: Frosting also occurs on the capillary tube inside the machine, and the current continuously rises from startup until the compressor overheats and shuts down. Releasing the refrigerant and replacing the capillary tube can solve the problem.
I've been repairing cars for over a decade and have encountered many cases of AC high-pressure line frosting. The most common cause is insufficient refrigerant. When the AC system lacks refrigerant, the pressure drops, causing the evaporator temperature to plummet and frost over. Another possibility is a stuck expansion valve, which disrupts refrigerant flow control and can also lead to high-pressure line icing. System blockages, such as desiccant clumping or pipe obstructions, may also be to blame. Ignoring these issues can result in poor AC cooling performance, increased compressor load, or even compressor burnout. My advice is to first use a pressure gauge to check system values and verify refrigerant levels. If low, locate and fix any leaks before recharging. Alternatively, try replacing the expansion valve. Addressing these problems early is the most hassle-free approach—don't wait until summer's unbearable heat strikes to take action.
My old car's AC keeps having issues. Last month, the high-pressure pipe frosting up gave me a scare. Only after taking it to a mechanic did I find out the refrigerant had completely leaked out. You can do a preliminary check yourself: after starting the AC, feel the high-pressure pipe—if it's icy hard and frosted over, and the cooling effect is poor, it's likely low on refrigerant or the expansion valve is broken. Don't underestimate this—it can reduce AC efficiency and damage the compressor. Turn off the AC promptly and get the pressure checked at a shop. For daily prevention, check the AC system's seal integrity before summer each year. If there's a significant leak, top up the refrigerant or replace parts. It saves money and gives peace of mind, ensuring no breakdowns while driving.
