What Causes Normal Low Pressure but Low High Pressure in a Car's Air Conditioning System?
2 Answers
Normal low pressure but low high pressure in a car's air conditioning system is caused by a malfunction or damage to the air conditioning compressor. This type of fault generally requires replacing the compressor with a new one. In a vapor-compression refrigeration system, the compressor is one of the main components. Its role is to pressurize gaseous refrigerant and then send it to the condenser for cooling and condensation. Below are the main reasons that can lead to compressor damage: 1. The air conditioning system is unclean, with particulate impurities being sucked into the compressor. 2. Excessive refrigerant or lubricating oil in the system, causing "liquid slugging" and damaging the compressor. 3. The compressor operates at excessively high temperatures or for too long. 4. The compressor lacks oil, leading to severe wear. 5. The compressor's electromagnetic clutch slips, causing excessive friction and high temperatures. 6. The compressor's power configuration is too small. 7. The compressor has manufacturing quality defects.
Over my many years of driving, I've frequently encountered situations where the AC has normal low pressure but low high pressure. This is usually caused by insufficient refrigerant or minor system leaks. Sometimes, when the AC compressor is worn out and lacks power, leading to reduced efficiency, it can also result in low high-side pressure. Another common issue is when the condenser surface accumulates too much dust or mud, impairing heat dissipation and preventing the high pressure from rising. A clogged or failed expansion valve, which controls refrigerant flow, is another culprit—when it malfunctions, high pressure drops. If air enters the AC system, the compressor operates unstably, and high pressure fails to build up. My advice is not to rush into DIY repairs when you notice these issues. Instead, take your car to a professional repair shop to check the high and low pressure readings, refrigerant levels, and system integrity. AC failure during scorching summer heat can be dangerous, so timely repairs save hassle and ensure safety. Safe driving comes first, and the AC system is a critical component for driving comfort.
