Why does the car air conditioner sometimes blow cold and sometimes not?
2 Answers
The reasons why a car air conditioner sometimes blows cold and sometimes not are as follows: 1. Excessive refrigerant: When the car is driving at high speed, the rotation speed is fast, and the pressure of the refrigeration system is high, the pressure controller (pressure switch) activates, causing the compressor to stop, and the air conditioning refrigeration stops at this time. When the car is driving at low speed, the rotation speed is slow, and the pressure of the refrigeration system is low, the pressure switch closes, the compressor works, and refrigeration resumes. Therefore, the refrigeration is intermittent. 2. Lack of Freon: The cause of this situation is usually a leak in the air conditioning system's pipes. At this time, you can drip some water at the joint of the car's refrigerant pipe, and bubbles will appear at the leak. Find the leak and repair it. Then remember to go to a professional car repair shop or 4S shop to add some Freon. 3. The filter is too dirty. Try to find the bypass valve on the filter base. When the pressure difference between the two sides of the valve reaches a certain value, it can be opened. Generally, the oil flows into the main pipe through the pipeline. Use a car-specific lubricant to lubricate other related components, and the situation will improve. 4. The air conditioning filter is aging: If the car air conditioning filter has been used for too long, it needs to be replaced.
When I drive my old car, the air conditioning often acts up, blowing hot and cold intermittently, which is quite annoying. The possible reasons could be insufficient refrigerant, leaks in the system causing loss of pressure, leading to inconsistent cooling. If the air filter is clogged, the airflow becomes irregular, especially in city traffic where dust accumulation worsens the situation. A stuck or faulty expansion valve can disrupt refrigerant flow, causing temperature fluctuations. I once tried adding refrigerant myself, but it didn’t help much. Later, a check at the 4S shop revealed loose wiring connections. Don’t ignore such issues—driving without proper AC is uncomfortable and distracting, and overheating can even impair safety. Start by checking simple fixes like the filter or topping up refrigerant; if that doesn’t work, seek professional repair. Spending some money is better than suffering in summer heat.
