Everyone has seen water or steam in headlamp housings. The logical assumption is, of course, that the headlight is simply leaking and therefore defective. But this is not necessarily the right explanation, because even high-quality headlamps with a high structural tightness can show this effect. Especially with modern LED headlights, this seems to occur more frequently.  

What is the most important lighting device on a vehicle? Quite clearly the main headlamp. And yet this topic is often treated stepmotherly. ...