What is the reason for refrigerant leakage after pressure testing shows no leaks in car air conditioning?

[WilliamAnn]

The reason for refrigerant leakage after pressure testing shows no leaks in car air conditioning is due to leakage at the charging valve, which requires replacing the charging valve before recharging the refrigerant. There are two methods for charging refrigerant in car air conditioning: one is high-pressure side charging, and the other is low-pressure side charging. Below are the specific introductions: 1. High-pressure side charging: Suitable for charging after leak detection and vacuuming. Note that this method requires the compressor to be turned off, the engine to be stopped, and the refrigerant tank to be inverted; 2. Low-pressure side charging: This method involves charging gas, characterized by slow charging speed, and is typically used for supplementing refrigerant.

[MacJuniper]

As someone who has been working with car repairs for years, I've encountered quite a few cases where leaks occurred after pressure testing showed no issues and refrigerant was added. The main problem lies in the pressure testing itself not being thorough enough, such as using too low pressure or insufficient testing time, which fails to detect tiny leaks. After adding refrigerant, the air conditioning system operates under significantly higher pressure, especially when the compressor is running, exposing previously hidden cracks or loose connections. Additionally, severely aged seals like O-rings can contract or expand due to temperature changes when refrigerant enters the system, worsening leaks. Vehicle vibrations during driving are also a common trigger, causing pipe connections to come loose. It's recommended to use high-pressure nitrogen during pressure testing to simulate actual operating conditions, pressurizing above the specified value and checking repeatedly. After adding refrigerant, don't rush to leave the repair shop; it's best to run the air conditioning for 30 minutes to monitor for leaks. Regular maintenance, such as replacing seals every two years, can greatly reduce such issues while also protecting the environment and health, as leaking refrigerant not only affects cooling but also releases harmful substances.

[SanKhloe]

I'm sharing from the perspective of an ordinary car owner, having personally experienced the frustration of an AC system that passed pressure testing but suddenly leaked refrigerant after recharge. When the pressure setting during testing is inadequate or the test duration too short, potential leaks simply don't show up. After recharge, the surging refrigerant pressure and operational pressure fluctuations can turn tiny cracks into major leaks. Aging seals are a common culprit - refrigerant exposure accelerates their cracking, and driving vibrations can loosen pipe connections causing leaks. I recommend professional shops for high-pressure dynamic testing, and suggest test-driving after recharge. Don't skip seasonal maintenance - inspecting AC systems and replacing vulnerable seals before season changes saves repair costs. Refrigerant leaks don't just waste coolant, they pose safety risks too.

[DiJayden]

As an auto mechanic, I explain this phenomenon: No leakage during pressure testing, but leakage occurs after adding refrigerant. The pressure test might have insufficient pressure or incorrect methods, failing to detect tiny leaks; after adding refrigerant, higher system pressure, temperature changes, or operational vibrations expose the leaks. Defective seals or refrigerant-induced aging can accelerate leakage. It's recommended to use high-pressure nitrogen for standard pressure testing and dynamically monitor system operation after adding refrigerant. Regular maintenance and O-ring replacements can prevent such issues.