Is the thicker or thinner car AC pipe the high-pressure one?
2 Answers
The thinner one is the high-pressure intake pipe, while the thicker one is the low-pressure pipe. Additionally, there are other methods to distinguish between high and low-pressure intake pipes: 1. By path: The low-pressure pipe runs from the evaporator to the compressor, while the high-pressure pipe runs from the compressor to the condenser, then from the condenser to the evaporator. 2. By letters near the compressor connection: Some compressors have letters like S or D marked near the connections to differentiate, where S stands for the low-pressure connection and D for the high-pressure connection. 3. By temperature: Start the car and turn on the AC, then feel the pipes with your hand—the cooler one is the low-pressure pipe, and the hotter one is the high-pressure pipe.
To be honest, I remember the car air conditioning pipes quite clearly, as I've been dealing with them for over a decade. In a car's air conditioning system, the thicker pipe is generally the low-pressure line, while the thinner one is the high-pressure line. This is mainly because the refrigerant coming from the compressor is under high pressure but has a small volume, so a thin pipe is sufficient—using a thicker one would cause waste and over-compression. On the other hand, the refrigerant returning from the evaporator has low pressure but a large flow rate, requiring a thicker pipe to move smoothly. From my experience repairing many cars, I've found that mixing up the pipe sizes can lead to system overheating or even bursting, which is a real headache. My advice is to check the thick pipe connected to the evaporator during routine inspections—it usually feels cool to the touch, while the thin pipe connected to the compressor may feel warmer. Knowing this distinction can save you a lot of hassle during maintenance and prevent damage to the air conditioning system.
