Here's a TSB for the Mazda 3: 09-024/03 2004 MAZDA3 - WATER DROPLETS / MOISTURE INSIDE FRONT AND REAR LIGHTS APPLICABLE MODEL(S)/VINS 2004 MAZDA3 DESCRIPTION After car wash or when driving in the rain, some customers may notice the outer edge of the headlights and/or rear combination lights become foggy due to water entry. This symptom appears at the sealing location of the light unit. Water is not trapped inside the lights which does not affect its function. The water droplets will evaporate and will not damage the light unit. DO NOT perform any parts replacement for this symptom as this is considered normal.