What Causes Ineffective Car Defogging?
4 Answers
First, determine whether it's external fogging. External fogging can usually be wiped away easily. If it persists, try spraying some windshield washer fluid. If it still doesn't clear, consider whether there's an issue with the wiper blades. For frost buildup, you can turn on the heater to blow warm air. Additionally, you can activate the air conditioning in defogging mode with the AC on, which should clear the fog quickly. If it doesn't clear completely, gently wipe the glass with a towel to check for any residue or foreign substances. Below are the functions of a car's air conditioning system: 1. Temperature Regulation: This is the primary function of car air conditioning. In summer, the cooling system produces cold air to lower the cabin temperature; in winter, except for large commercial vehicles that use independent combustion heaters, most vehicles rely on residual heat for warming. 2. Humidity Control: Humidity significantly affects passenger comfort. Cabin humidity should generally be maintained between 30% and 70%. Standard car air conditioning systems do not regulate humidity—only through ventilation or advanced luxury car systems with integrated heating and cooling. 3. Airflow Adjustment: The speed and direction of airflow greatly impact comfort. Direct airflow should be limited to a certain range when the temperature is appropriate, and the speed can be adjusted based on passengers' living environment, age, health, and temperature preferences. 4. Air Purification: Cabin air quality is crucial for comfort.
I get really annoyed when I can't clear the fog while driving, especially on rainy days when blurred vision is dangerous. There are quite a few common reasons, like not selecting the correct defogging mode on the AC, or using recirculation mode which traps moisture. A dirty air filter can block airflow, greatly reducing the AC's dehumidifying effect. Another issue could be the windshield itself – if there's a thick layer of oil film or dirt, the defogging air won't disperse the dust. If the AC isn't cooling enough, it might be due to refrigerant leakage causing low system pressure. Poor electrical connections or a faulty blower can also result in weak airflow. My advice is to regularly clean the windshield and check the AC, develop the habit of adjusting settings before driving, and address any issues immediately to avoid sudden accidents on highways that could endanger the whole family.
I've dealt with quite a few cases of failed car defogging, mainly originating from the air conditioning system. If the compressor isn't running or there's insufficient refrigerant, the dehumidification capability directly deteriorates. A faulty thermostat causes erratic temperature fluctuations, preventing cold air from blowing out. When the humidity sensor malfunctions, the system makes incorrect judgments and fails to automatically defog. Aging connection wiring may cause short circuits, rendering the fan inoperative. Damaged window heating functions are also common, especially in winter. Owners can first try increasing the fan speed and switching to external air circulation. If there's no improvement, replace the filter or seek professional repair. After all, heavy fogging that obstructs road visibility can lead to major accidents. Ensure power is disconnected for safety before any manual intervention.
When I first started driving, I often encountered issues with the defogger not working properly, and I found that most of the time it was due to operational errors. Either I didn’t press the front windshield button, or the temperature was set too high, which didn’t help with dehumidification. If there was oil residue on the glass affecting visibility, simply wiping it a few times with a cloth and glass cleaner would do the trick. A dirty or clogged filter could also reduce ventilation efficiency, but it’s easy to remove and clean it yourself. If the air conditioner is leaking refrigerant and needs a recharge, it’s best to leave it to a professional shop. Don’t delay—clearing the fog promptly ensures clear visibility and smooth driving.
