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This is NOT a VW dealer being awkward, they are following the VW instructions and if they replace the headlight THEY will have to pay for it out of their small margins as VW will throw it back at them so have a little patience and understanding! This is THE official VW word on the matter
Technical product information Transaction No.: 413101/17
Service info: headlamps leak/steamed up Release date: 24-Jan-2012
Customer statement / workshop findings
Customer statement:
• Exterior light leaks/steamed up.
Technical background
Under unfavourable conditions, e.g. a car wash in winter, the inside of modern clear glass lamps steam up, sometimes persistently.
Customers complain about this because they fear leaks and effects on the function and service life of the lamps as well as MOT failure.
Production change
- - (i.e. NONE!)
Measure
Visible steaming-up of the lamp glass is a concept-related characteristic of modern lighting systems, which affects all manufacturers and has no effects function or service life:
• It is no sign for water ingress as the result of a leak.
• Because of the materials used corrosion can be ruled out
• No loss of light or dazzling as the glass dries up after switching on the lamps.
Replacing the headlamps does not fix the problem.
A groundless parts replacement will be redebited.
Air humidity or leak?
The glass must be clear about 30 minutes after switching on the lamps.
If this isn't the case or drips run down the inside of the glass, check the lamps for leaks.
Make sure that the cap fits correctly.
Customer information
Air humidity tends to settle on cold surfaces. When switched on great heat is created in the lamps which is released via the vents (open system). If the lamps are switched off, they cool down and cold, humid air is sucked in via the ventilation. The air settles as condensation on the coldest point from the inside on the glass. On the lamps this is mainly the glass. This is a normal physical process. This has always been the case, but has been less or not at all noticeable on the old type of glass.
In stationary or when driving the condensation passes off.
But the condensation may recur.
Whereas the light passage area of the glass dries quickly when the light is on and especially when driving, this takes sometimes longer around the edge and the customers suspect a complaint. Technically this remaining steaming-up is insignificant.
But what are the reasons for this slow thawing?
On modern lamp systems with clear glass the light is not aligned by the lens any more but through a lens system and a reflector. The light beam hits the centre of the glass and it takes therefore longer this the edge of the glass warms up. As a result, the thawing is slower towards the edge of the glass.
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