Polywave,

Whilst I agree that drilling holes may not be an ideal solution (and shouldn't be the solution) there is some sense in it, believe it or not!

Without going too much into physics (bear with me!) I'll try and explain to the best of my knowledge . . .

[geek mode on]
As you may know, a constituent of air is water vapour. When air is cooled, it reaches a temperature known as it's dew point. This is where the air reaches it's saturation point. At this point, the water vapour in the air condenses and becomes visible (the reason why we get clouds!)

Ok, so we don't get clouds in the headlights! During the cooler months of the year, you will have noticed dew on the grass. This happens when the moisture has no mixing effect from the wind to create clouds so it appears as moisture (dew) on your car, the grass etc. This is, effectively, what is happening in the headlights.

The parcel of air sealed inside the lights is reaching it's dew point as it cools and is appearing as moisture on the glass. By drilling holes into the casing, this equalises the pressure (which also has an effect on the dew point) of the air inside with the air outside and also equalises the relative humidity. This should mean that it is much more difficult for the moisture to form within the lights (but could, as you say, let other moisture in!) As pointed out in the first post, after turning your headlights on, the moisture should clear pretty quickly - this is because the air is being heatedback above the dew point! (We all know how warm the lights get).

So . . . where does that leave us? Well, it seems to me that during the manufacturing process of the headlights, they should be sealed in specially prepared dry environment thus preventing any moisture being "trapped" within the lights. It would appear this hasn't happened in many cases (hence our problem!)

Now that we know this . . . what's the solution? Drilling holes will only hide the problem, as descibed above. In my opinion, what we need are sealed units that have been properly sealed in a dry environment. Perhaps there is a dealer "fix" to replace the air within the units with drier air or maybe they have some other solution - hence my post on here.
[/geek mode off]

Hope I haven't bored you with that explanation! If anyone can come up with an alternative solution, I (and many others, I'm sure) would be only to pleased to hear about it!

Regards,

Clive