What are the potential consequences of an excessively open automotive AC expansion valve?
2 Answers
An excessively open expansion valve manifests as higher-than-normal air temperature from the vehicle's cooling vents. The low-pressure side pressure becomes elevated (normal high pressure should be 15-20 kg/cm², low pressure 2-3 kg/cm²). Increased suction pressure leads to higher suction temperature, which in turn raises the discharge temperature. Excessively high discharge temperature poses significant risks to compressor lubricating oil and coil insulation, ultimately causing compressor damage. Below is additional relevant information: Automotive AC: Officially termed automotive air conditioning system. It regulates and maintains optimal cabin temperature, humidity, air purity, and airflow to provide passenger comfort, reduce travel fatigue, and create favorable driving conditions that significantly contribute to road safety. Typically consisting of refrigeration, heating, and ventilation systems, this integrated unit maximizes limited vehicle interior space with simple structure and user-friendly operation, representing the internationally prevalent modern automotive AC system.
Last week when I helped a friend fix his car, I encountered a situation where the expansion valve opening was too large. If adjusted too high, the refrigerant flow would surge into the evaporator, causing the temperature there to drop excessively and quickly form ice or frost, completely blocking heat exchange. This would result in no cold air coming out of the AC vents, leaving the car interior still stuffy and uncomfortable. The compressor would also have to work overtime, with the load skyrocketing, making a buzzing sound like an old ox panting. Over time, it could overheat and burn out. I quickly checked and adjusted the expansion valve setting to the standard position, which improved the situation. Otherwise, fuel consumption would also skyrocket, and the system pressure imbalance could affect the lifespan of other components. Don’t overlook this small part during regular maintenance.
