What Causes Fogging Inside Car Lights?
2 Answers
Temperature differences and improper car washing or wading through water can cause fogging inside car lights. Fogging due to temperature differences: A vent pipe is installed on the rear cover of the headlight assembly, allowing hot expanding gases to escape. However, sometimes moisture can enter this vent pipe, causing slight fogging. This phenomenon typically occurs in winter, rainy seasons, or foggy weather. Fogging caused by car washing or wading: Besides temperature differences, improper car washing or wading through water is a more common cause of fogging inside headlights. When cleaning the engine, use a damp cloth instead of a high-pressure water jet. Methods to remove fogging inside car lights: When drivers notice fogging inside the lights, they should first determine the cause. If it's due to temperature differences or humidity—for example, after prolonged use of the lights at night—the fogging will usually dissipate after turning on the low or high beams for about 10 minutes. For fogging caused by car washing or wading, promptly turn on the lights to allow the moisture to evaporate. Drivers should not ignore persistent fogging and should regularly check the condition of their car lights.
Having driven for over a decade, I've noticed that fogging in car headlights is quite common. It's mainly caused by temperature and humidity. When you turn on the headlights at night and it suddenly rains, the cold rain hitting the hot lens creates a temperature difference that leads to condensation inside. Headlights aren't completely sealed either - they're designed with ventilation holes for heat dissipation, which can let in moisture during humid weather. I once experienced aging of the rear cover gasket where car wash water seeped through gaps and formed fog clusters. However, if the fog dissipates on its own within half an hour, it's generally fine. But if you see water droplets sloshing inside or fog persisting for days, you should check for cracks in the lens or damaged seals. Long-term water accumulation can easily damage bulb circuits, so don't take it lightly.
