BMW 3 Series - Headlight condensation

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Sun 15 Dec 2013 11:54
BMW 3 Series - Headlight condensation - tony g
Hi ,
My daughters 2007 318d saloon has developed severe condensation in both headlights .
I've removed the bulbs and seals on both sides ,dried out the interior of the lamps using a hair dryer ,but the problem returned soon after .

Has any other member come across the problem and resolved it .Is it possible to remove the headlamp glass and reseal it ?

If I was to drill a small hole in the rear of the headlamp assembly ,to allow air to circulate freely ,would that resolve the problem or make it worse .

There are no chips and no damage to the headlamps .

One small point , don't lose the small wishbone shaped spring clip that holds the bulb in place .BMW dealers charge £5 for that 3" long shaped piece of steel wire !
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Sun 15 Dec 2013 12:34
BMW 3 Series - Headlight condensation - gordonbennet

Depending on how easy, or not, the headlights are to remove could you take them out completely and gradually submerse the lenses in a bowl of water to see where the leak is coming from...probably not but would it be possible to jerry seal a tyre inflator to the empty headlights in situ then blow (carefully) into the housings whilst spraying them with soapy water as you would checking for a puncture, might find the leak that way might be a lot of faff for no joy, just a suggestion...don't blame me if it doesn't work..;))

If not then i expect there is a break in the bonding between glass (hopefully) but more likely plastic lens and the headlamp unit casting...unless you can spot a likely suspect water trap/leak point in the unit casting.

Seems to be standard lamp manufacture now to be clear plastic bonded on, why they are so expensive to replece i don't know, one thing is certain they don't last decades like real traditional headlights with glass lenses.

By the way i did the same as you, drying out etc over several hours on daughters Aygo, within a week just as bad...3 years old Toyota fitted new headlamp units under warranty without a moments hesitation.

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Sun 15 Dec 2013 14:13
BMW 3 Series - Headlight condensation - bathtub tom

The problem with drying them using a hair dryer is the warm air could hold quite a lot of water vapour.

When I had this problem, I waited until a day when the relative humidity was low (you need some way of measuring it). Remove the bulb and holder, use the hair dryer on warm, blowing it inside the headlamp. Do this for some time after all the condensation disappears. Turn the hair dryer to cold and continue to blow it in the headlamp until everything is cool. This way you ensure the headlamp is filled with cold, dry air which is capable of holding less vapour than warm air.

This method worked for me for several years, but I notice condensation's starting to return on the inside of the lens on particularly cold and wet days. I presume the air inside the headlamp expands and contracts when the lights are used and the air inside gradually becomes more humid due to the vent in the bulb holder. I guess there has to be a vent somewhere in the headlamp to allow the air to expand and contract as it warms and cools.

Unless of course you do have a hole in headlamp that's allowing water in.

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Sun 15 Dec 2013 15:41
BMW 3 Series - Headlight condensation - Andrew-T

Seems to be standard lamp manufacture now to be clear plastic bonded on, why they are so expensive to replece i don't know, one thing is certain they don't last decades like real traditional headlights with glass lenses.

They are expensive because one can't buy a cheaper one anywhere else !

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