Question

Why did the AC in my car stop blowing cool air after several hours of a long drive in 90+ degree heat but work normally after being shut off overnight and then stop blowing cool again after driving several more hours the next day in the same temps?

Answer 1

There are several potential reasons why your car's AC system might behave this way, with intermittent cooling issues during long drives in hot weather. Some common causes include:

1. Overheating of AC components: Extended operation of the AC system can cause certain components, such as the compressor or condenser, to overheat. When these components get too hot, they may fail to function correctly, resulting in reduced cooling performance. After the car is shut off and allowed to cool down overnight, the system may work normally again until it overheats during the next extended drive.

2. Refrigerant Leak: If your AC system has a refrigerant leak, it can result in a gradual loss of refrigerant during extended operation. When the refrigerant level drops too low, the AC may stop blowing cool air. After the car is parked and not running, the system pressure stabilizes, and it may work normally again until the refrigerant level drops again during the next day's drive.

3. Frozen Evaporator Coils: Prolonged use of the AC system in high temperatures can sometimes lead to the evaporator coils freezing up. When the coils freeze, airflow is restricted, and the AC stops blowing cold air. After the car is turned off, the ice on the coils melts, and the AC may work fine again until the coils freeze up once more.

4. Electrical Issue or Sensor Problem: There could be an electrical problem or a faulty sensor within the AC system. Electrical issues can cause intermittent cooling problems, and sensors that are not functioning correctly might provide inaccurate readings, affecting the system's performance.

5. Fan or Blower Motor Problems: The fan or blower motor that circulates the cool air throughout the cabin could be malfunctioning. If the fan stops working during the drive, you might experience a lack of cool air.

6. High Ambient Temperature: In extremely hot weather, especially above 90 degrees Fahrenheit, the AC system might struggle to maintain the desired cooling level, resulting in reduced performance.

It's essential to have a qualified mechanic inspect and diagnose the AC system to identify the specific cause of the intermittent cooling issue. They can perform tests, check for leaks, examine electrical components, and address any necessary repairs. Regular maintenance of your car's AC system can help prevent such issues and ensure it functions optimally, especially in hot weather conditions.