Is it acceptable to only evacuate the low-pressure side of a car's air conditioning system?
3 Answers
No, it is not acceptable. Below is relevant information: Evacuation: Evacuation refers to the process of removing air from the car's air conditioning pipelines, while also extracting water vapor from the pipelines. This is because the refrigerant in the air conditioning system is highly sensitive to moisture. If there is air or water in the pipelines, the air conditioning system may fail to cool or provide insufficient cooling, affecting the comfort of passengers during summer. Therefore, to ensure the system operates correctly, evacuation must be performed before adding refrigerant. Purpose of evacuation: The evacuation of a car's air conditioning system aims to remove environmental moisture-laden air that enters the system when it is opened for maintenance. If refrigerant is already present in the system, evacuation is not necessary when topping up. In the absence of a vacuum pump, a portion of refrigerant gas can be added from the high-pressure side, and then released from the low-pressure side until a slight cooling sensation is felt.
I once encountered someone who only evacuated the low-pressure side when repairing a car, resulting in very poor cooling performance. The air conditioning system is a closed loop, and evacuating is meant to remove air and moisture. If only the low-pressure port is evacuated, the air in the high-pressure side can't escape, leaving bubbles trapped inside. Residual moisture can corrode the pipes, and refrigerant mixed with air reduces efficiency, even increasing fuel consumption. The correct method is to use a high-low pressure gauge set, connect both ends, open the valves, and evacuate with a vacuum pump for 15-20 minutes until the pressure gauge stabilizes at a negative value. Don't cut corners, or you'll have to redo the repair, wasting time and money. Driving in summer without AC is unbearable, so I recommend going to a professional shop to get it done—safe and hassle-free.
I once tried evacuating only the low-pressure side of the car AC, which immediately caused cooling issues. Residual air in the high-pressure side led to uneven refrigerant mixing, forcing the compressor to overwork – resulting in rapid fuel consumption and strange noises. Prolonged operation like this risks refrigerant leaks (environmental hazard) and four-figure repair bills. AC failure during hot weather driving is dangerously unsafe. The correct method requires connecting gauge sets to BOTH high and low ports, evacuating until achieving full system vacuum (minimum 15 minutes). Routine maintenance should include vacuum checks. Since adopting this proper approach, my AC runs smoothly with zero part replacements – highly practical knowledge.
