I have 'misty' headlight covers and I have cleaned them with 1200 paper, then 2400 paper, then toothpaste. They still have a mist in them. The outside is absolutely smooth now (it was quite rough). Could they be dirty inside - or even within the material? What I see is not condensation - but could it be residue left from previous condensation? Is this cleanable?

Be careful, the lenses have some kind of coating on so once you have wet sanded them and polished them up the finish doesn't last very long before you need to do it again. I think there may be some sort of sealant you can apply to make the finish last longer.

 

Regarding the mist on the inside, I think your right in thinking its been left by condensation possibly and dirt/dust in general. However I have some double glazing that has gone all cloudy as there must be air ingress between the panels but I have never seen any condensation in them.

This might help you decide.

 

Ive cleaned plenty now, only had a few with marks and damage on the inside, a quick polish with G3 has always sorted them.

 

I also wet sand up to 3000 before polishing with a machine polisher and G3 cutting compound.

 

 

Thats going up 400 at a time roughly. some images are the same grit but by hand and others with machine polisher and the final image is polished,

Edited 30 March, 201610 yr by hutchysrs50

I have 'misty' headlight covers and I have cleaned them with 1200 paper, then 2400 paper, then toothpaste. They still have a mist in them. The outside is absolutely smooth now (it was quite rough). Could they be dirty inside - or even within the material? What I see is not condensation - but could it be residue left from previous condensation? Is this cleanable?

N/S headlight unit on the missus's car has this issue, along the lower quarter, maybe, definitely on the inside of the plastic.  Assumed it will need a new headlight in due course. I may have to have a chat to Mr Hutchy by the sounds of it?

Any time

So how easily does the front plastic bit come off Hutchy?  Job for a muppet like me, or needs skill?

If its the polo i woudlnt bother PM sent anyway

No, Fabia.  Funnily enough the N/S headlight on the Polo was boogered when I bought it (melted bulb holder area), but new unit from ECP fixed that.

This might help you decide.

 

Ive cleaned plenty now, only had a few with marks and damage on the inside, a quick polish with G3 has always sorted them.

 

I also wet sand up to 3000 before polishing with a machine polisher and G3 cutting compound.

 

 

Thats going up 400 at a time roughly. some images are the same grit but by hand and others with machine polisher and the final image is polished,

How do you remove the covers - and, more importantly, put them back again?

Are you sure you have simply not polished away the sanding marks?  It normally takes more than toothpaste to cut away the sanding marks.

As said, the top right picture, second one in will be with around 2400 grit and it's still cloudy. It's only after the 3000 and cutting compound with G3 they polish up clear.

As for opening then, most people put them in the oven to heat them then prise them apart with screw drivers etc

Are you sure you have simply not polished away the sanding marks?  It normally takes more than toothpaste to cut away the sanding marks.

Yes, I am sure. There is a distinct edge to the misting that has not changed since I cleaned it. On the offside, it is approximately the lower third where it is misted. On the nearside, it is a smaller patch in the middle. MOT coming up on Tuesday!

If your local I'm more than happy to split them for you

As said, the top right picture, second one in will be with around 2400 grit and it's still cloudy. It's only after the 3000 and cutting compound with G3 they polish up clear.

As for opening then, most people put them in the oven to heat them then prise them apart with screw drivers etc

Is that to break a seal, or to get some expansion? How do you re-assemble? Not the freezer, I presume! (Based in Bristol, btw)

Edited 30 March, 201610 yr by Mike Austin

Other side of the country then.

Well if you wanted to post them to me I can polish them all properly anyway, can lacquer them as well so they never faid again.

Anyway! It's a soft glue seal that gets softer as it heats so when putting back together just heat them back up and force the lens back into place. If the seal is damaged or missing anywhere buy a roll of Butyl and reseal, it will prevent condensation in the future also.

I've seen people use silicone... I wouldn't advise it but that's up to you

That edge is probably remnants of the UV protection layer.  I've found this appears on fairly mild refurbs I have done and the only way to clear them is fully remove the UV protection.  Often that's 600 grit paper to start

 

I'd be interested to see pictures.

I use 400 grit to remove it then move up from that.

That edge is probably remnants of the UV protection layer.  I've found this appears on fairly mild refurbs I have done and the only way to clear them is fully remove the UV protection.  Often that's 600 grit paper to start

They feel very smooth. Would I not feel the edge with my nail?

I'd be interested to see pictures.

I will post a pikkie or two tomorrow.

RHS was cleaned all over, but contours of some 'mist' still visible, plus some speckles:

 

 

LHS was roughly attempted, but the contour of mist in the centre still visible:

 

Looks like it's still the Coating on the outside of the light. It will feel smooth even thought it has different layers, 2400 is fairly smooth!

I suggest you get some 600 grit and do the full light for a while and then move your way up to 3000 before you polish.

Has anyone heard of an MOT failure due to misty headlights? Mine is coming up in the next few days.

Has anyone heard of an MOT failure due to misty headlights? Mine is coming up in the next few days.

Absolutely. Most people who come to me are due to failing or advisory on lights uv damage. It affects the beam test at the mot

Edited 31 March, 201610 yr by devonutopia

This is the affected one on the missus's car. Thought it wasn't a good enough pic to show it at first, but then I spotted the line of the top edge of the mistiness on the inside of the plastic; I've highlighted it with a few black arrows:

 

This is the affected one on the missus's car. Thought it wasn't a good enough pic to show it at first, but then I spotted the line of the top edge of the mistiness on the inside of the plastic; I've highlighted it with a few black arrows:

 

Now that looks identical to mine, only not so extensive. Time spent on any size of grit, polish, toothpaste or wax on the outside will be wasted.

I have an MOT on Tuesday. The good news is that I just dropped in to ask them if they would fail it on the headlights, and they said "No". So a stay of execution ...

Yep, ours passed this month with no advisories about headlights.

It's more cosmetic than anything, I reckon.