What Causes High Pressure in Car Air Conditioning System?
2 Answers
Here are the reasons for high pressure in car air conditioning system: 1. Air in the system - the system should be completely evacuated and refrigerant should be refilled. 2. System blockage - mostly caused by expansion valve blockage or malfunction, the expansion valve should be replaced. 3. Excessive refrigerant - manifests as "hot" feeling at the exhaust port, "warm" feeling at the suction port, and occasional liquid hammering sound from the compressor. The system should be completely evacuated and refrigerant should be quantitatively refilled. 4. Poor condenser cooling - manifests as "hot" feeling in the pipeline from condenser outlet to expansion valve inlet. 5. Expansion valve failure - manifests as large amount of dew or frost on the low-pressure pipe. High pressure occurs because gaseous refrigerant cannot be completely converted to liquid to reduce volume, while the compressor continuously discharges high-temperature and high-pressure gas.
I remember one time in the workshop, I encountered a car with high AC system high-side pressure. The owner complained about slow cooling and increased fuel consumption. The most common issue is poor condenser heat dissipation—if the fan is faulty or the radiator fins are clogged with dust or leaves, heat can't dissipate, causing the pressure to spike. Another possibility is overcharging the refrigerant, which overloads the system and naturally raises the high-side pressure. System blockages, such as a stuck expansion valve or a clogged receiver-drier, can also restrict flow and lead to increased pressure. Additionally, hot external conditions, like a scorching sunny day, make it easier for the pressure to rise. If high-side pressure isn't addressed promptly, AC efficiency drops significantly, and the compressor may even get damaged. So, I advise car owners to regularly clean the radiator, check the fan operation, and not let minor issues turn into major repairs.
