Headlight Misting Up

D

DAZ A4 GONE

Member
My nearside headlight unit is misting up.I have removed light,dried it out with a hair dryer,applied clear silicone sealant around the outside of where the two halves of the unit join and after a few days it has misted up again.Anyone had similar? Can it be fixed or do I need to replace it? Thanks in advance, Daz.
 
All headlamps mist up. It's especially noticable with the modern clear lenses. At the back of the headlamp there is a vent allowing the lamp to breathe. This is vital as when the lamp is on the air inside expands, and when off it contracts. The change in pressure is so great that without venting there is even a risk of exploding or imploding.

I'm not sure how the ventilation is on the A2 lamps. Often a rubber tube is used located on the rear to allow air to move freely but prevent water ingressing. Of course water vapour will enter the lamp in the air and this is the case for every lamp on every car.
 
I find it goes after a long run in the dark with the lights on, unfortunately this seems to be every weekday at the moment!
 
Hi Daz A4 Gone,

My nearside headlamp misted up too. I don't know why. It eventually went away after a few months. Again, I don't know why. The good news is that it didn't come back.

John.
 
Quite simple really, outside temprature, non too warm at the moment, lights on most of the time = heated air inside light unit, which forces air out through the vent, lights cool off = air contracting drawing in air from outside which at the moment is full of moisture which then condenses on the coldest part = plastic lense.
Only way around this is to run a pipe from the vent to above the radiator then when lights cool warm air is drawn from over the rad, this will be of a lower moisture content and will reduce misting.
 
Anyone ever tried putting a packet of those silicone granules you get in electrical equipment packaging into the back of the cluster to dispel the moisture? Reckon it'd work!?
 
Some light manufacturers are looking into silica gel. It's really not a new problem, only that the problem is now obvious with the introduction of clear lenses. Lights need to breathe and so all cars have this problem. What makes things worse is the modern trend for larger lamps. The cold spots are larger and this is where the condensation builds. The weather we are enjoying now does not help - lots of rain and cooler. The air is carrying more water - specially to mist up our headlamps!
 
Some members had this problem a few years ago and Audi even changed some headlights under warranty.

They should not get condensation in them, neither of our A2s did and I don't remember having a car that did. Must be a sealing problem somewhere!
 
There has been alot of talk about this issue but no definite conclusion.

The condensation in my light seemed particularly bad last night. I recently changed the headlights. Could this have been the reason for it?

Given that electricity and water don't mix that well (or maybe they do but at the detriment of all appliances) is it likely to damage the car?

Any help you could give in dealing with it would be appreciated.

On the way to work this morning I noticed alot of cars with condensation inside the lights but none as strikingly bad as mine. Also, it was even. Not simply in the driver's side unit as mine is.
 
As I said before all lamps need to be vented in order to function. Unfortunately this means that moisture will always be present more in some lamps than others due to the thermodynamics and the effects of cold spots where the hot lamp is not able to get hot drying air to reach the far corners. Condensation shows up more with the fashionable clear lenses of todays cars than the older style but was just as present before as now.

A solution would be LED lamps. I think BMW have started to fit these at the rear of the 3 series coupe. LED lamps throw out little heat and don't need to be vented and can therefore be fully sealed - should have no moisture. But how much these will cost?
 
More Misting

My Offside light is always misting up as well. There is some sort of fan underneath the light assembly that runs after the engine i sturned off. Could this be the cause of moisture ingress ?
 
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