What are the possible reasons for low high pressure in car air conditioning?
3 Answers
Possible reasons for low high pressure in car air conditioning are as follows: 1. System aspects: Refrigerant leakage, refrigerant blockage, dirty heat exchanger, etc. can cause low high pressure in car air conditioning. 2. Electrical aspects: When the compressor, solenoid valve, four-way valve, or motor operates abnormally, it can also lead to low high pressure in car air conditioning. 3. Heat dissipation: When the air conditioning is operating normally, the low pressure is about 3bar, and the high pressure is about 15bar. Note that this is when the air conditioning is operating normally, with the cabin blower set to the fourth gear, and the radiator cooling fan running at high speed, indicating good heat dissipation from the external condenser.
With years of experience in car repair, I've found that low high-side pressure in the A/C system is most commonly caused by insufficient refrigerant. The car's A/C system is like the human circulatory system—when refrigerant is low, the high side naturally can't build up pressure. Other causes include internal leaks or wear in the compressor, preventing pressure buildup; a clogged condenser or poor heat dissipation, which traps heat and lowers pressure; or faults in the expansion valve, blocked filter-driers in older cars, or malfunctioning sensors providing incorrect readings. Low high-side pressure leads to poor cooling performance, making summer drives feel like a steamer—prompt inspection is crucial. I recommend regular A/C maintenance with professional pressure testing to prevent minor issues from turning into major repairs. For DIY checks, start with refrigerant levels and connections, always prioritizing safety.
Last time when my air conditioning cooling effect deteriorated, I took it to the shop and found out the high pressure was low due to a refrigerant leak in the system. From my experience, when the low-pressure refrigerant is insufficient or leaking, the high pressure naturally drops. Other possible causes include insufficient compressor pumping or the condenser fan not working, leading to poor heat dissipation. Remember to check the wiring connections, as loose connections can also affect the pressure. Low high pressure will result in higher outlet air temperatures, making long drives very uncomfortable. It's best not to delay repairs until winter; get it checked early. I usually recommend starting with the simpler checks, like measuring the refrigerant level and pressure values.
