Why does the air conditioning cool when accelerating but not when idling?
2 Answers
The reasons why the air conditioning cools when accelerating but not when idling: Poor condenser heat dissipation: You can rinse the condenser with water when washing the car or take it to a quick repair shop to blow the condenser with an air pressure gun. Also, check the refrigerant pressure at the same time. Excessive refrigerant: When accelerating, the compressor speed increases, and the high pressure rises. Due to excessive refrigerant, the high pressure becomes too high, causing the high-pressure protection switch to trip and stop cooling. Conversely, when driving at low speeds, the high pressure remains normal and does not trigger the high-pressure protection, allowing the compressor to cool normally. Excessive dirt in the refrigeration oil: This can clog the filter screen of the filter, reducing the cooling effect and increasing resistance. The flow of refrigerant to the expansion valve also decreases, leading to the car air conditioning not cooling. Sometimes, if air enters the car air conditioning system, it can cause excessive pressure in the refrigerant pipes and poor refrigerant circulation, which also results in insufficient cooling.
This is actually a quite common issue. After driving for several years, I found that the compressor is driven by the engine. When you press the accelerator and the engine speed is high, the compressor spins faster, resulting in better cooling performance and colder air from the AC. At idle speed without pressing the accelerator, the compressor has almost no power, leading to poor cooling performance and less cold air. This could be related to belt tension—if it's too loose, it might slip—or it could be due to insufficient refrigerant or blockages in the system affecting circulation. I recommend regularly checking the tightness of the AC belt and the refrigerant level, and replacing aging parts early to avoid bigger problems. While driving, try accelerating to see how the AC responds. If the cooling fluctuates between hot and cold, take it seriously—safety first, don’t wait until it breaks down to fix it.
