What Causes Hissing Sound and No Cooling in Car Air Conditioning?
3 Answers
Car air conditioning producing a hissing sound without cooling indicates an issue with the compressor, which is responsible for cooling and is also the source of the abnormal noise. When the car air conditioning is in cooling mode, the compressor clutch engages, allowing the engine to drive the compressor. The compressor continuously compresses the refrigerant and delivers it to the evaporator. Inside the evaporator, the refrigerant expands and absorbs heat, cooling the evaporator. The cooled evaporator then cools the air blown by the blower, allowing cold air to be discharged from the air conditioning vents. The car air conditioning system is designed to cool, heat, ventilate, and purify the air inside the cabin, providing a comfortable environment for passengers, reducing driver fatigue, and enhancing driving safety.
The air conditioning starts hissing and stops cooling, something I've experienced several times, mostly caused by leaks in the refrigeration system. The hissing sound often occurs near the evaporator or compressor, which is the sound of refrigerant escaping through small holes. Once it's all leaked out, there's no cooling effect. Possible causes include aging and cracked hoses, worn seals, or a condenser punctured by a stone. Last year, a friend's car had this issue—the sound was particularly noticeable at idle. Later, at the repair shop, they found a loose fitting, replaced the part, refilled the refrigerant, and it was fixed. If not addressed promptly, the compressor may run dry and burn out, doubling the repair costs. I recommend first checking the pipes for signs of oil stains or moisture, common indicators of leaks. However, it's best to have a professional shop use a pressure gauge to test and confirm the issue, then address it quickly to avoid driving in unbearable heat during summer.
Having driven for over a decade, nothing is more frustrating than when the air conditioning acts up. A hissing sound accompanied by poor cooling is usually due to insufficient refrigerant. The hissing resembles the sound of gas leaking and may come from beneath the dashboard; the weak cooling is caused by inadequate pressure, disrupting normal circulation. I remember last summer during a long drive when the AC suddenly made those noises a few times before giving out—turned out to be a tiny pinhole leak in the evaporator. Causes vary: corroded pipe joints, system overheating leading to expansion valve failure, or worn compressor blades. I tried checking for oil stains along the pipes myself, but the technician used specialized tools to pinpoint the leak during repairs. Don’t delay—if the evaporator or compressor fails, it could mean major repairs. Driving without AC, especially on highways, increases fatigue and distraction, so pull over promptly for checks or schedule a repair shop visit.
