Is it normal to have water droplets or fog inside the taillight?

[Declan]

It is not normal. The specific situations are as follows: 1. Winter temperature differences: Large temperature differences in winter can cause condensation inside the headlights. In the structure of the car headlights, there is a vent pipe connected to the outside. 2. Purpose: The purpose is to allow the expanded gas inside the headlight to be discharged through the vent pipe when the headlight is turned on and the temperature rises. After the headlight is turned off, the temperature drops, and the internal pressure difference increases, drawing in outside air through the vent pipe. This can draw in humid air, causing condensation and fog inside the headlight. Additional information: Fog is likely to form after heavy rain or car washing, especially if care is not taken during washing and water is sprayed directly at the engine compartment or headlights with a high-pressure hose, allowing water droplets to flow inside. When the vehicle is driven through water, the engine and exhaust system, being significant heat sources, can generate large amounts of water vapor when rain falls on them. Some of this water vapor can enter the headlights through the vent pipe.