Hole in headlight

One of my headlights is full of condensation


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Evening

Any advice where to drill a hole to let condensation out of a headlight?

Thanks
The latest advice is not to drill any holes and use a hair dryer into the back of the headlight, to remove any moisture, and then reseal the cover using vasolene etc around the rubber gasket . Rightly or wrongly I have drilled a couple of very small holes, just underneath the clear front lense, into the black plastic surround at each end which seems to have worked. Be careful not to go in too deep though. 🤞
 
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I’ve always drilled a few 10mm holes in the underside of the outer plastic. Always keeps them clear and condensation free.
 
That reminds me to drill holes in the spoiler on these.

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Drilling a hole will let the condensation out, but why not find how the moisture is getting in and fix the problem rather than the consequence?

Condensation is usually one of the following...

Rear cover incorrectly fitted / missing or seal damaged / missing.

Small hole in the glass due to stone chip. Or someone drilled a hole in the wrong place!

The join between the glass and the rear housing sealant has failed ( internal seal if splittable lights ). Either split the lights or externally reseal.

Note the headlights do have an inbuilt venting system to take care of minor condensation. This can be boosted by fixing a couple of small bags of desiccant to the inside of the rear cap.
 
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Thanks guys I don't know which light I have but will take it out and check the body for gaps and seals missing. Any images of where holes drilled would be great.
 
Before you drill holes, try following method. it worked with me. I got a pair of headlights from Valeo. On the day i replaced them with the old ones, it was rainy and humid. I left the lights cover open for quite some time, since i have to put all the bulbs in and change the motor. When headlights were on, with all the lights switched on, and rain was pouring on the lenses, they immediately start to condensate.

I tried many methods how to get rid of condensation.
- First i dry them with all the lights on (long, main, position) and with open covers - after some time, closed the covers - no go
- than i add the hairdryer. I hairdryed them for about 5 minutes each - no go
- I put the headlights in an oven on 50C with the thermo/humid meter in, and let the humidity drop to 20%. Get the headlights out and leave them in the room until they cool down. Closed the covers and put them on the car. All was fine, until the first time, lights were on for a longer time. When i switched them off, after 5', condensation start. So - no go
-repeat all the mentioned methods, and always seal the covers (i used hand creme) - no go
- put silicagel and rice in a sock, and put it inside the headlight. - no go

The results were always the same. When the lights were on long enough to get warm, immediately after switching them off the condensation start.

Than i spent some time thinking about this problem.
The point is, that the air inside the headlight chamber gets very warm. When lights are switched off, and if its cold outside, condensation will start on the lense (from inside), specially if the air inside the headlight has high humidity. Bigger the humidity, bigger the condensation.

So this leads us to following conclusions;
- if trying to hairdry or dry with lights on (or both methods) we will always get to same situation, this is warm on the inside/ cold on the outside and as a result condensation
- ideally we would need SAME temperature on the inside and on the outside, just that the air inside the headlight chamber has as low humidity as possible. Vacuum would also be fine, but how to achieve this?!?

With this in mind, i waited for a cold and dry day. Strong dry NE wind was blowing for a couple of days and the air humidity dropped on 31%. The outside temperature was 6C. I left the covers of the headlights open, to let them dry. The covers were left open a day or day and a half. After this i sealed the covers (again with hand cream) get them closed and for now, i had no condensation jet. I did this three days ago. It is still pretty dry ( 40%) and cold (6C). On Friday will start raining, and than i will have all the answers. But from theoretical point of view, i thing this last method has good chances to work. Will keep you posted.

One more word about sealing.
What is the point of sealing, if there is a ventilation valve (that grey square thing on the edge of the headlight, right where the blinkers are). Sealing/resealing is only when the rain/water is entering inside the headlamp.

Hope it helps, cheers, Andrej
 
Edd, thanks closing off this thread, I too have the same problem, the one headlamp is coming out for a leveller motor replacement anyway, so I’ll drill both with a 6 or 8mm while I’m there the same as you and @Dave M
 
Please do not drill holes. Find the problem and solve it. If Audi wanted holes they would have done so. By drilling holes you are masking the problem and that in turn may cause more issues especially with the bulbs.

Remove both rear covers, check the gaskets are not damaged or twisted and remove them. Fit the gaskets back into the opposite side to how removed. This will rotate the gaskets in their slots. Apply a light smear of silicone grease to the seal and ensure the cap is correctly seated and locked in place.


If the condensation is bad, remove the headlight from the car and remove all the bulbs, range motor and the wiring. Now fill the headlight with clean water and place "glass" down. If there is a leak from the glass to housing seal area or a hole in the glass the water will leak out. Mark the area the water was seen coming out and empty the light and thoroughly dry it out. If splittable then a new seal is required if one piece then either warm in the oven to split them and internally reseal OR externally seal around the the leaking area ( better to seal the complete circumference )

Note when drying out the headlight never touch the reflector as you will damage it.
 
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