Removing condensation from headlamp

14
Found 3rd Jun 2015
My nearside headlamp must have a gap in the seal as I have a fair amount of condensation build up.

This was enough to fail the MOT as it restricted the light being output by the bulb (not noticable when driving though!).

The headlight unit has two internal enclosed focusing units for the bulbs which I can only just access, but I can't get to the glass at the front where the moisture is.

Any ideas as to how to clear the moisture? I think an entire replacement head unit will be over £100 including the labour.
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You might be able to evaporate it out. In the past I've seen people leave a lamp with an incandescent bulb pointing at the glass for a few hours, but a hairdryer or heat gun might do the job.
Original Poster
Thanks, but the only way I could do that is by heating the glass directly, but given it's proximity to the plastic bumper I'm not sure is wise. However, I'll give it a try and switch it off if things get too hot.
I would have thought switching on the head lamp at full beam would provide enough heat to evaporate the moisture if their is a hole for the moisture to escape as they get quite warm.
The same happened to my BMW a few years back. It was one massive sealed unit and would have cost over £200 replace.

Instead I just got a hairdryer out, removed the little cap at the top of the unit and blasted hot air down it for a while to remove the condensation and build up of water in the bottom of the unit. Do this right before you take it back for a retest otherwise if you do it and leave it overnight, chances are it will collect condensation again.
Edited by: "NEtech" 3rd Jun 2015
Had this problem with mine...

Hair-dryer on warm at first to evaporate the moisture. Once its all evaporated, switch the hair-dryer to cool to blow out the warm moist air and cool the headlamp back to atmospheric temperature. That way the warm air wont draw back in the moisture due to the temperature difference.

Works perfectly if done like that.
Original Poster
Well, firstly I only have a heat gun, secondly - I can't get hot air inside the unit.
It's a '97 model and 'sealed' (apart from the hole that caused the condensation that is).

There is no cap at the top to remove, there are two clips, but they just there to prevent movement.

I tried removing what I could from the back of the unit, but due to an incredibly small space to undo a phillips head screw I can't remove the housing that is used to focus the beam - that blocks the whole back of the unit.
Bigfootpete

Well, firstly I only have a heat gun, secondly - I can't get hot air … Well, firstly I only have a heat gun, secondly - I can't get hot air inside the unit. It's a '97 model and 'sealed' (apart from the hole that caused the condensation that is).There is no cap at the top to remove, there are two clips, but they just there to prevent movement.I tried removing what I could from the back of the unit, but due to an incredibly small space to undo a phillips head screw I can't remove the housing that is used to focus the beam - that blocks the whole back of the unit.



There is the hole for the bulbs take them out before the hair dryer, might need to buy a cheap one or borrow but obviously don't use the heat gun. Might be cheaper and easier to find a headlight in a scrap yard or eBay
As above, I removed the large headlamp bulb and blew in warm air using a hairdryer
We used to get this a lot on ford pumas, the best way to deal we found was to drill a 3mm hole at the very bottom of the front lens (these were poly-carbonate) no further problems.

Also beware using a heat gun as a lot of modern headlights have the lens set in a gel seal which is very easy to soften with not to much heat.
Edited by: "Argoj" 3rd Jun 2015
drill a little 5mm hole in the bottom so it all runs out
Banned
Drill a hole in the bottom of the light behind the bumper so no one can see it and it will work a treat. Tried on a c3 and not had a problem since....well i say that it is a citroen lol.
Original Poster
eslick

There is the hole for the bulbs take them out before the hair dryer, … There is the hole for the bulbs take them out before the hair dryer, might need to buy a cheap one or borrow but obviously don't use the heat gun. Might be cheaper and easier to find a headlight in a scrap yard or eBay



To clarify, the whole unit has two internal units within the whole thing - the bulb goes into the internal units - there is no access to the glass that is external - I can only access the back of the internal focussing units - they are shaped like a large bulb themselves. Blowing heat into them has no effect on the external glass.

I tried just heating the glass last night and it cleared the condensation enough to get it through the MOT.

I'm not sure about the drilling - I can't access underneath unless I take off the bumper, but I don't have anywhere I could do this.
Cover the light completely with ally foil and turn on headlights on high beam with the engine running until cleared.
I then drilled a couple of small holes (carefully ) through the top of the headlight and placing a short piece of plastic tube just inside the headlight a sticking out about 3mm and sealing it from water ingression with blue tack or similar.
Learnt a lot today. Probably never need it but who knows ? X)
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