What causes low low pressure and high high pressure in car air conditioning?

[SimonRose]

The reason for low low pressure and high high pressure in the air conditioning system is poor circulation in the system. Focus on checking the following aspects: clogged capillary tube (or expansion valve), such as dirt blockage or ice blockage. Clogged dryer filter. Kinked connection pipes causing flow obstruction, shut-off valve not fully open, four-way valve not properly aligned, or dirty condenser tubes. Here are the relevant details: 1. Measure the high and low pressure of the air conditioning system while the engine is idling. 2. The normal high pressure for car air conditioning should be 1.3-1.7MPa (13-17kg/cm2 or Lbf/in2); the normal low pressure should be between 0.1-0.25MPa (1-2.5kg/cm2 or 15-35Lbf/in2). If the low pressure is higher or lower than this range, it indicates improper adjustment of the expansion valve. Compressor issues are not included in this category. When the engine throttle is increased, the measured low pressure should decrease with engine speed—the faster the speed, the greater (faster) the pressure drop. This indicates good compressor performance; otherwise, it suggests a compressor fault. 3. Note that car air conditioning pressure is highly dependent on ambient temperature (the working environment of the condenser).

[LaValentina]

I've repaired many car air conditioning systems, and the condition of low pressure on the low side and high pressure on the high side is quite common. The main cause is usually a clogged expansion valve. The expansion valve controls the flow rate of the refrigerant. Once it gets blocked, the pressure on the high side shoots up, while the pressure on the low side drops significantly, resulting in the air from the AC not being cold at all. It could also be due to excessive dirt accumulation in the dryer or the entire system getting air or moisture inside, disrupting the normal cycle. If you notice the AC performance deteriorating, you should promptly check the expansion valve and dryer, and replace them if necessary. Don’t delay too long, as pressure imbalance can damage major components like the compressor and condenser. For regular maintenance, it's best to clean the AC filter once a year to prevent contaminants from entering.

[EloiseMarie]

Last time I drove, I encountered an issue with the AC not cooling. At the repair shop, they found low low-pressure and high high-pressure readings. The mechanic checked and said the expansion valve was clogged, probably due to my lack of regular maintenance and too much dust buildup. After replacing the expansion valve, the AC immediately returned to normal. The whole process was quite simple and didn’t require much professional equipment. Now, I make sure to check the AC pressure before summer, buying a pressure gauge to measure the high and low-pressure values to see if they’re within the normal range. A reminder to fellow drivers: don’t neglect regular maintenance, otherwise refrigerant leaks or system contamination can easily cause such troubles.

[OJustin]

When encountering low low pressure and high high pressure in the air conditioning system, it's mostly due to a faulty expansion valve. The expansion valve controls the refrigerant flow rate. If it's blocked, the high pressure will rise while the low pressure drops, affecting cooling performance. Other possible causes include system blockage or insufficient refrigerant. As a car owner, avoid disassembling it yourself. Have a professional check the high and low pressure values to determine the cause before repairs. The basic solution is to clean or replace the valve to ensure smooth refrigerant circulation. Regularly changing the cabin air filter can help prevent such issues.

[SanJasmine]

To address the issue of low low-pressure and high high-pressure in the AC system, follow a step-by-step approach. First, check if the high and low-pressure values are abnormal. If the low pressure is too low and the high pressure is too high, it may indicate a blocked expansion valve. Inspect whether the valve is stuck or dirty, and then confirm if there are any blockages in the dryer and the entire pipeline. Minor issues can be resolved by cleaning with tools, while major problems may require component replacement. Also, pay attention to the compressor's operation, as abnormal pressure could damage it. It's recommended to visit a reliable repair shop for a comprehensive inspection. After repairs, recharge the system with the appropriate amount of refrigerant to restore the AC to its optimal condition.

[DeVivienne]

Low suction pressure and high discharge pressure in the air conditioning system are typically caused by a clogged expansion valve. This pressure imbalance not only reduces cooling efficiency but may also lead to pipe bursts or compressor failure. I've seen many cases where neglect of maintenance caused dust or moisture accumulation. It's recommended to inspect the AC system quarterly, especially the pressure balance. Keeping the dryer clean and using the correct refrigerant type is crucial. This extends AC lifespan and improves driving comfort. By the way, pressure issues become more dangerous during hot seasons - timely repairs prevent safety hazards.