Headlamp condensation

[Chas]

Interesting stuff here

http://www.wipo.int/pctdb/en/wo.jsp?WO=2001/055636&IA=WO2001/055636&DISPLAY=DESC

Later, when the vehicle is parked and the lamp is turned off, the ambient temperature inside of the lamp housing gradually cools, and the air left in the housing contracts, thereby lowering the pressure inside the housing and drawing fresh external air into the housing through the vent (s).

When conditions outside the lamp housing include a high level of humidity, the replacement air drawn into the housing is humid air, which may contain tiny suspended water droplets and/or evaporated water in the gas phase.

As the lamp housing continues to cool, moisture, from humid air which has been newly drawn into the lamp housing, may precipitate and condense out of the air to form liquid water, and such water may be deposited on the internal surfaces of the housing.

Once a high level of moisture becomes established inside of a lamp housing, it may persist and be difficult to get rid of, because the vent hole or holes are relatively small, and turning the lamp back on may cause re-evaporation of liquid condensate within the housing. A cycle of condensation and evaporation inside the lamp housing may follow, without significantly reducing the humidity level therein. Repetitive cycles of evaporation and condensation, under the above-described conditions, may actually exacerbate the problem and promote deterioration of electrical components of the lamp.

 

[c240yaz]

Looks like you found the answer to your original queerie, on the link you posted ? well done

 

[portzy]

By portzy

"My SLK does this now and then and its more pronounced at this time of year, certainly more so after she's had a wash.

I tend to get the couple of inches along the bottom just like you as in this picture but the dealer has said its perfectly normal. What I do is leave the engine running with the headlights on for about ten or fifteen minutes and it dissapears completey."


Is there any clouding on the lense when they are dry Dave? I will send you some satchets for your headlamps if they work ( they are only about 1" x1")

cheers

Chas

ps the centre caps look good, thanks

Hello Mate.

Nope, looking at them right now when its very humid, but generally dry, the lenses are perfectly clear. They would stay that way unless I give them a wash with warm/hot'ish water then the inside of the lense will cloud exactly to the extent as in the picture.

The breathers at the back are clear and the misting will go after about ten minutes with the headlights on. In the warmer months there is no problem at all, just late autumn/winter. All that said though, and in a certain light, I can see slight water marks on the inside of the lenses that I think may have been there from day one. I did intend to strip the lights out at one point and clear the insides but with them being bi-xenon I'm reluctant to do this. No-one else notices but me so I'm not that fussed.

Glad about the discs being ok and a couple of the silica bags would be welcome, as an experiment.

Cheers.

Portzy.

 

[Chas]

Now I am armed with all this knowledge, I have just spent 30 mins in the dark(with torch ) and rain trying to find the air vent at the back? of the headlamps. I can't seem to find it, can someone give me a range and bearing from the pic below of headlamp rear as to where it might be located?

thanks

 

[Seamster15]

My Porsche does it also.... but the Seat does'nt!

Since having a Baby (14 weeks ago) I've decided that life is way too short to worry about such things and I shall instead sleep!!!

 

[BTB 500]

Now I am armed with all this knowledge, I have just spent 30 mins in the dark(with torch ) and rain trying to find the air vent at the back? of the headlamps. I can't seem to find it

I was thinking about this last night ... whilst I can understand why a vent might be needed, why would the rear covers then have rubber seals etc. to make them airtight?

 

[Chas]

"My Porsche does it also.... but the Seat does'nt!

Since having a Baby (14 weeks ago) I've decided that life is way too short to worry about such things and I shall instead sleep!!!"


I am just thinking of all the dosh I will earn when I cure this problem for headlamps
Just wait till baby is 17 like my daughter, and wants driving lessons
But yes,alas you are right, I am just bored, waiting to go on a night shift

 

[Chas]

I was thinking about this last night ... whilst I can understand why a vent might be needed, why would the rear covers then have rubber seals etc. to make them airtight?

I suppose the bulb covers are there to prevent moisture/dirt getting on to the electrics. I think the vent is very small and designed to only let a little air in and out.
So small my middle aged eyes can't see the dam thing

 

[c240yaz]

The rubber seals are to prevent water entering the unit. Air will always find a way in, even through the microscopic spaces in the wiring connectors, bulb seats and via the seals.

 

[television]

If one examines the double and triple rubber seals for houses that do not have sealed units it important that there are two gaps left,a small one in one bottom corner and a small one in the opposite top corner so that air can pass through. Failure to observe this results in misted windows. In cars you cant have a hole in the top as water would get in, but what I am trying to say is that it requires two holes to work. Doing any work on them this weather does not help, and could make it worse

The air this weather is very heavy and moisture laden

 

[BTB 500]

The air this weather is very heavy and moisture laden

77% humidity outside at the moment, according to my wireless weather station thingy

 

[Chas]

Ok found the air vent, its on the back of the projector dipped beam cover, easier to see in daylight !!
pics below.
Hopefully the silica gel satchet inside this cover will do the trick!!

 

[MBManInKen]

Hopefully the silica gel satchet inside this cover will do the trick!!

Would it not block the vent?

 

[Chas]

Would it not block the vent?

No, I'll stick it inside the headlamp between the projector and the cover, or double tape it above the vent near what looks like a figure 1 in the second picture. If that doesn't work I'll experiment puting it in different places within the headlamp.

COPYRIGHT has been applied for

 

[BTB 500]

Won't the silica simply absorb moisture from the atmosphere through the vent?

 

[Chas]

Won't the silica simply absorb moisture from the atmosphere through the vent?

Err..... that is exactly what silica gel desiccant is meant to do, and hopefully by absorbing the moisture present in the air within the headlamp will stop the condensation


Desiccant
From Wikipedia, the free encyclopedia
A desiccant is an hygroscopic substance that induces or sustains a state of dryness (desiccation) in its local vicinity in a moderately-well sealed container.( in this case a headlamp)

http://en.wikipedia.org/wiki/Desiccant

 

[c240yaz]

Silica Gell packets will absorb a lot of moisture quickly, you will need to replace it very often.

Consider that Silca Gell packets are used in sealed bags, from manufacturing plants to customer delivery, very common with the shipment of electronic circuit boards etc. to absord any moisture trapped in the packaging while intransit.

As the headlight unit is not sealed from the atmosphere, it will be a continuall absorbtion of moisture from the circulating air. The Silica will not take long to reach it's max absorbtion.

Personally, I don't think it is worth the trouble to keep replacing this.

 

[television]

As c240yaz completely, do bare in mind that we are only affected during this time of the year

 

[Chas]

Unfortunately its very wet on the west coast up here which is under the influence of the Gulfstream (warm moist air), and combined with global warming, very heavy and short lived downpours are common, summer or winter. It might not work, but it only takes a minute to place or change a satchet, and clouding in the inner lense at the bottom is already present in my headlamps (6 months old).
Personally I don't want them to get worse (I like my car and take pride in it). I am just not content to do nothing.

Nothing ventured, nothing gained

 

[television]

Unfortunately its very wet on the west coast up here which is under the influence of the Gulfstream (warm moist air), and combined with global warming, very heavy and short lived downpours are common, summer or winter. It might not work, but it only takes a minute to place or change a satchet, and clouding in the inner lense at the bottom is already present in my headlamps (6 months old).
Personally I don't want them to get worse (I like my car and take pride in it). I am just not content to do nothing.

Nothing ventured, nothing gained

The further in the lamp that you can get it the better, and that is agreed by all, you are like me, so never give up