What Causes the Freezing of a Car Air Conditioner's Evaporator?
3 Answers
Here is a detailed introduction to the freezing of a car air conditioner's evaporator: Expansion Valve: The adjustment of the expansion valve is too small, resulting in excessively low low-pressure. Refrigerant: The system has insufficient refrigerant, leading to excessively low evaporator pressure. Internal Circulation: The internal circulation filter is clogged. Temperature Control Failure: The temperature control (or temperature sensor) malfunctions, causing the compressor to run continuously. Variable Displacement Compressor: The energy control valve (pressure regulating valve) of the variable displacement compressor fails, causing the compressor to operate at full capacity continuously, resulting in excessively low low-pressure and freezing of the evaporator.
Evaporator coil freezing usually occurs due to an imbalance in the air conditioning system. For instance, when refrigerant levels are either excessive or insufficient, the temperature drops too rapidly, leading to icing. I've handled numerous similar cases where a faulty or stuck expansion valve was the culprit, as abnormal refrigerant flow causes abrupt temperature drops in the evaporator. Dirty filters are another common cause, restricting airflow and trapping heat, which leads to condensation buildup and eventual icing. Control system malfunctions can also be problematic, such as when the compressor runs continuously without cycling off. This icing phenomenon occurs more frequently in high-humidity conditions. If not addressed promptly, it can reduce airflow or even block it entirely, making driving particularly uncomfortable in hot weather. In severe cases, it may damage the compressor, increasing repair costs. To prevent this, regular maintenance checks and ensuring proper cabin airflow are recommended.
I found that when the evaporator freezes, it directly affects driving comfort and safety. The sudden reduction in airflow, leaving only a weak cool breeze, makes the cabin unbearably stuffy. During high-intensity driving, such as long-distance highway trips, the soaring interior temperature can lead to fatigue or heatstroke. More critically, freezing can cause the compressor to overwork or even burn out, shortening the AC system's lifespan and leading to costly and troublesome repairs. Additionally, melted ice may seep into electronic components, corroding wiring. To address this, I immediately turn off the AC and switch to warm air for a few minutes to defrost when encountering such issues. Regularly, I set the temperature not too low—around 23°C is ideal—and avoid prolonged AC operation in highly humid areas to prevent ice buildup, ensuring safe and reliable driving.
