[downunderbmer]

Hi, I have sanded both headlights, starting with 400 grit and working my way up to 3000 grit, using a rotary sander. The results are uneven with fogginess along the lower part of the headlight? What could be the reason for this and could you recommend a possible fix? Many thanks.
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[grannyknot]

I would say your rotary is spinning too fast, it creates heat that can smear the plastic of the lens.
Slow it down and let the grit do the work without heat.

[tracer bullet]

Agreed. It could be uneven pressure as well. Grit and pressure both will change the effect of the sanding, so be sure to be consistent. I always finish any sanding with a particular grit with a light pressure.

Also be sure it's uniformly wet, if the inside or outside is dry with the other wet you could also get uneven results.

I'd also put a 2nd layer of tape down, it can be easy to burn through it accidentally with the edge of the pad while you're focusing on a different area.

[Redd]

When you sand the headlight covers you're actually removing the top anti-UV clearcoat on the cover. The dull grey area is clearcoat that you have not sufficiently removed. You need to spend more time sanding those areas.

[stbm5]

ive messed with this before, these solutions just dont work great.

[Raimo5]

Originally Posted by Redd

When you sand the headlight covers you're actually removing the top anti-UV clearcoat on the cover. The dull grey area is clearcoat that you have not sufficiently removed. You need to spend more time sanding those areas.

That. Seen it many times before. Old clearcoat is not fully removed.

[Ralph III]

Hello OP,
I agree with the others. It does indeed look like clear coat that hasn't been fully removed? What was your intentions with this project? Because if your intentions were always to apply a new clear coat, you shouldn't be using any sandpaper over 800 grit. The new clear coat will not adhere properly to a very fine surface and you could expect premature failure. You want to use a grit between 600-800 for the clear coat which is what most manufacturers recommend.

Using very fine sandpaper, such as 3000 grit, would only be used on lenses with very minor fading. In that instance, you are just removing the very top layer of faded clear. You'd then follow that up by buffing it out to a pristine finish. The goal is to limit the amount of clear that is removed, in order to preserve the remaining clear, in that instance.

So, working from 400 grit up to 3000 grit is fruitless and/or a very poor plan. I'm a former professional Detailer, btw. I've made many such corrections. At this point, you just need to finish removing the rest of the clear and then apply a new clear. Good luck and let us know how it turns out.

Ralph