What is the intermittent hissing sound from the car air conditioner?
2 Answers
Car air conditioner intermittent hissing sound is the noise of refrigerant flowing in the radiator. Here is the relevant introduction about car air conditioner refrigerant: 1. Working principle: When the air conditioner is operating in cooling mode, the low-temperature and low-pressure refrigerant gas is compressed by the compressor into high-temperature and high-pressure refrigerant gas. The high-temperature and high-pressure refrigerant gas releases heat in the condenser (generally air-cooled, i.e., the heat dissipation copper pipe of the outdoor unit) and turns into medium-temperature and high-pressure liquid (the heat is carried away by the outdoor circulating air). The medium-temperature and high-pressure liquid then passes through the capillary tube to expand and reduce pressure, becoming low-temperature and low-pressure liquid. The low-temperature and low-pressure liquid refrigerant absorbs heat in the evaporator (indoor unit copper pipe) and evaporates into low-temperature and low-pressure gas (indoor air is cooled by passing through the heat exchanger surface). 2. Refrigerant charging method: Under normal temperature and pressure, R410A is a chlorine-free fluorinated alkane non-azeotropic mixed refrigerant, appearing as colorless gas stored in steel cylinders. Based on the characteristics of R410a, an application practice was conducted to replace HCFC22 with R410a in a room air conditioning system, including theoretical analysis and system matching. Experimental results show that under the same conditions, compared with HCFC22, the heat transfer coefficient increases, flow resistance decreases, and after system optimization matching design, the performance (COP) is significantly improved, reaching the European market Class A energy efficiency level.
The car's AC intermittently makes a 'hissing' sound like air being released. This is usually due to a minor issue with the expansion valve. When the valve that controls refrigerant flow gets stuck, it releases pressure unevenly, creating intermittent noises. It could also be caused by insufficient refrigerant or air entering the system, leading to uneven refrigerant flow and noise. I've personally encountered this issue—a friend's car had a corroded and clogged expansion valve, which resulted in gradually worsening AC cooling and increased fuel consumption. It's best to take it to a professional repair shop promptly. Technicians there will use specialized tools to check pressure and test valve functionality. Ignoring the problem can lead to compressor overheating and damage, resulting in higher repair costs. With frequent AC use in summer, such issues can easily be overlooked, but fixing them ensures quieter and more comfortable driving while reducing unnecessary energy waste.
