Why is the high pressure of car air conditioning low?
2 Answers
This may be caused by a blockage in the high-pressure pipeline before the expansion valve, or it may be due to the expansion valve's opening being too small. The car expansion valve is a main component of the car air conditioning refrigeration system, installed at the inlet of the evaporator, serving as the boundary point between high and low pressure in the system. If it fails, it can lead to abnormal low-pressure conditions—either too low or too high. Below are the main functions of the expansion valve: 1. Throttling effect: High-temperature, high-pressure liquid refrigerant is throttled through the expansion valve's orifice, becoming low-temperature, low-pressure mist-like hydraulic refrigerant, creating conditions for refrigerant evaporation. 2. Controlling refrigerant flow: Once the liquid refrigerant enters the evaporator, it evaporates into a gaseous state, absorbing heat and lowering the temperature inside the car. The expansion valve controls the refrigerant flow to ensure the evaporator's outlet is entirely gaseous refrigerant. If the flow is too high, the outlet may contain liquid refrigerant, potentially causing liquid slugging in the compressor. If the refrigerant flow is too low, it may evaporate prematurely, resulting in insufficient cooling.
As an ordinary car owner, I've found several common causes for low high pressure in the air conditioning system: First, refrigerant leakage leads to insufficient pressure on the high-pressure side and poor cooling performance. Second, wear and tear on the AC compressor reduces power output. Third, condenser blockage causes poor heat dissipation and pressure drop. Fourth, pipeline or sensor malfunctions. I remember that long drive when the AC suddenly stopped cooling - turned out to be refrigerant leakage. After spending some money on recharging the refrigerant, it worked again. Regular maintenance and pre-summer AC system checks can prevent unexpected failures. Low high pressure not only affects driving comfort but may also increase fuel consumption - definitely not worth the trade-off. I recommend timely diagnosis at professional repair shops.
