Why does the car air conditioner sometimes cool and sometimes not?
4 Answers
There are several reasons why a car air conditioner may sometimes cool and sometimes not, including a broken drive belt, a covered condenser, improper operation of the blower fan, or insufficient refrigerant. Broken Drive Belt: Check if the drive belt is broken or loose. If the drive belt is too loose, it will slip, accelerate wear, and fail to transmit power. Also, check for any noise inside the compressor. Noise may indicate damaged internal components, and internal wear can prevent effective compression. Covered Condenser: Check if the condenser fins are covered with dust. If the condenser fins are covered with dust, the efficiency of the condenser will be significantly reduced. Improper Operation of the Blower Fan: Operate the fan at "low, medium, and high" speeds. If there is any abnormal noise or the motor is not functioning properly, it should be repaired or replaced; otherwise, the airflow will be insufficient. Insufficient Refrigerant: If you see a large number of bubbles through the sight glass, it indicates insufficient refrigerant. If you pour water on the condenser to cool it and still see no bubbles in the sight glass, it indicates an excess of refrigerant.
Last time my car's AC had the same issue, blowing hot and cold which was really uncomfortable. The most common cause is insufficient refrigerant - when it leaks, the pressure gets too low causing the compressor to cycle on and off. Another possibility is moisture in the AC lines freezing and blocking the expansion valve, then working again when the ice melts. A faulty compressor clutch with poor contact can also cause intermittent operation. I suggest first checking the refrigerant pressure gauge readings - abnormal high/low pressures indicate a leak. A dirty cabin air filter can also affect cooling performance, and that's something you can replace yourself. If those check out fine, it's best to have a shop inspect the electrical system and compressor. A friend of mine once had issues with poor contact in the compressor relay.
Intermittent cooling in car air conditioning is quite common, and I've just researched it these days. There are mainly three possible causes: first, insufficient refrigerant, where the compressor automatically shuts down for protection when the pressure drops; second, moisture entering the air conditioning system, which can freeze and block the pipes, causing an ice blockage; third, a fault in the compressor itself, such as clutch wear or excessive internal piston clearance. Additionally, a dirty condenser leading to poor heat dissipation can also cause the compressor to overheat and shut down. I recommend first using an air conditioning pressure gauge to check the high and low pressure values. If the readings fluctuate repeatedly, it's likely a refrigerant issue. You can try cleaning the condenser fins yourself, but if that doesn't help, the compressor should be inspected and repaired promptly.
Intermittent air conditioning issues are indeed frustrating. This situation is most likely due to insufficient refrigerant or a leak. When the compressor can't draw enough refrigerant, it automatically shuts off for protection. It could also be caused by a failed dryer bottle leading to frozen and blocked pipelines, which then work again once the ice melts. Another possibility is an electrical issue, such as poor contact in the pressure switch or a faulty thermostat. I remember that cleaning the radiator can help to some extent, but for a complete solution, it's best to have a professional check the refrigerant pressure and compressor condition. Don't delay too long—driving without AC in summer is unbearable.
