My 2005 XKR lights have been modified to include 3 drain holes in the underside of each unit. Both lights fill with condensation in Scottish winter when humidity is 100%. I’ve not spotted anything in the threads so far. Anybody got any further ideas? not sure that desiccant is going to help. There don’t appear to be any leaks/ ingress points for rainwater to enter.

View oof 3 drilled ventilation holes from underside.

Torch illuminating drain holes.

 

It has been a problem for quite some time. Assuming it is condensation I would think that some vent holes would be better placed higher rather than lower.
The XK150s don't seem to suffer from this and they have two vent tubes placed in the rear portion of the housing and above the mid point.
My 2005 had the base h1 headlights, I changed the lows to hi intensity and the high beam to an led. The led has a fan for cooling the circuit...I didn't have a fogged headlight after this conversion. Maybe the air circulation and the small gaps in the rear (to facilitate the HiDef assembly) was enough to keep it clear?
wj

 

Thanks for this. My conclusion is that the condensation results on inside glass because, when external temperature drops, the inside is relatively warmer and suspended moisture condenses on inside of lenses a bit like some UK bedroom windows. That leaves few options; keep moisture out, dehumidify or keep it in suspension. None of these seem practical. My additional holes appear to offer little more than drainage and a bit more, but not enough, ventilation. Am I missing something on the benefit/purpose of the vent tube in reducing condensation or anything else?

 

Back in the early 80's our (US) shop installed Euro (glass lens) headlight assemblies into some 100's of cars. They never fogged up, but they were not in a semi sealed environment.
Add a small computer fan (maybe from a graphics card) to move the air and a desiccant pac to absorb?
wj

 

I love this YouTube channel for his work on the XK . Have a look at his solution.

 

That's a very good find. Thanks very much as I hadn't seen it before