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Discussion Starter · #1 ·
My husband and I own a 2002 Classic Prius whose headlights are getting very foggy. I've cleaned the outside plastic part with both Windex and vinegar with no noticeable results. I think that there is dirt on the inside of the plastic cover. But we can't figure out how to get these covers off. All we managed to do was break one little plastic hook that holds the plastic covers in place.

So....anyone know how to remove the plastic covers of the headlights?
 

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I don't know what material was used on the Classics, but Windex/ammonia is bad for lexan, which is used on the current model. I use ammonia-free window cleaner and then use 303 Aerospace.

Most plastic lenses fade with UV exposure and turn milky or yellow. At some point they must be replaced. Cleaning won't get rid of the fog in that case.
 

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There is more to a headlight these days than just a lens. A little history.

Starting in the mid-80s, manufacturers started to move away from sealed beam headlights to bulb based headlamps. This was mostly due to the a desire to create a more sleek and areodynamic front end on vehicles without having to engineer expensive specially shaped sealed beam headlamps (not that some manufacturers didn't do just exactly that).

These headlamp assemblies were a lens, along with a reflector, all in one unit. They were generally made entirely of different plastics, but the clear portion (usually Lexan) and the reflector/bulb housing were welded together at a place which was not visible on the exterior of the vehicle. This created a lens/reflector like a sealed beam, but with a hole for the bulb assembly to be inserted and locked on.

So, here is the issue for you. The lens isn't removable because it is an integral part of the reflector assembly. To remove the lens, requires removing the entire headlamp assembly. Since the lens is not attached by screws or some other fastener to the reflector, but rather is welded to the reflector, if there is dirt on the interior of the lens, the whole assembly has to be replaced.

These assemblies are not cheep. You may be able to find some used from a wrecking yard, but considering how many Prii from either generation are on the road, the only candidates for used parts are probably going to be wrecked cars and finding undamaged headlamp assemblies on vehicles that have been in frontal collisions is going to be minimal. If you can find a car that was rear-ended or side swiped, you have a better chance, but again, finding a wrecked Prius isn't exactly an everyday occurance.

Until the lens is actually starting to yellow, which is what Lexan does over time, I wouldn't worry about replacing the lens or about any scratches.
 

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I had a situation where my Nissan had front/driver side damage, requiring one lens assembly to be replaced. It noticably mismatched the one that wasn't replaced due to age and slight hazing of the lens. The body shop was able to get the old one to look much better by buffing the old lens.
 

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Discussion Starter · #5 ·
Thanks for the information, guys! I feel much smarter (and dumber for using Windex) now.

I guess that the "milky film" isn't THAT big a deal. I just get jealous whenever I see a Prius on the road whose headlights are pristinely clear.
 

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Check that the lens isn't cracked. A crack might have let in moisture which condensed on the inside surface (this happens to one of my foglamps). A bad gasket on the bulb itself can also let in moisture. A hair dryer treatment through the bulb opening, then a sealant on the crack, can clear up some cases of "fogged" lenses.
 

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Okay, a desperate last ditch measure, but...

Sometimes the "fogging" is really just a scratched and pitted surface. If the surface is just pitted, scratched, but otherwise intact (not yellowed), what about a coat of clear polyurethane spray? It's UV resistant, fairly durable, and will "smooth" all the pits and crazing, so light may pass better.

Might work well enough while you check junkyards for a rear-ender, and replace the unit cheaper than a new part form the dealer.
 

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The lens on emergency lights of fire trucks and other emergency vehicles often become cloudy due to scratches, dirt, etc. Most places that sell emergency lighting carry lens cleaning products which work very well. Here are a couple of links. You could give them a call to see if they carry the product and ask if it will work on headlights.

http://www.jtechlighting.com/index.html

http://www.galls.com/index.html
 

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I've had excellent results restoring badly pitted/hazed headlight lenses using a combination of wet sanding followed by machine polishing with light cut and then fine polish.

First step is to mask of the lenses with blue 3M masking tape, unless you plan to shoot some clearcoat over them when you're done, in which case you should remove the reflector assemblies from the car. Then wet sand with 1000, 1500, and then 2000 grit sandpaper. Then I apply Menzerna Intensive Polish and Final Polish II with a 4" orange cutting pad mounted in a cordless drill. Takes just a few minutes and the lenses sparkle like new. At this point you can shoot some clearcoat over the lenses for protection, but I don't bother, I just make sure they get a coat of Zaino sealant next time the car is detailed. Painting the lenses with clearcoat will greatly extend the time before the lenses need another restoration, but since sanding and polishing them is not a big deal to me, I never do it.

Meguiar's Plast-X could be used in the place of the polishes I use. I have some and it doesn't have as much cutting power, nor does it leave the surface with as much gloss, but it is cheap and widely available, and most people can achieve satisfactory results with it. I have not been impressed with the headlight lens restoration kits they sell at auto parts stores, though I have heard the one sold at Napa auto parts works pretty well.
 

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Plastic polishes have two stages.
The first is a fine abrasive that will eventually take the entire surface down to the bottom of the scratches, leaving it smooth. The trick here is to not let the plastic heat up while you are polishing it. I've used ethyl alcohol as a coolant/lubricant while polishing light pipes for nuclear research - it works very well. It takes a long time to polish a large surface such as a headlamp, so be patient. Use cotton batten/balls as a polishing pad - the medical variety. Replace the pad often.

The second part is a wax that fills the scratches, leaving a smooth surface. This only lasts a short time, of coarse.

Finally, you can get the 3M "clearbra" to cover headlamps. It makes them more rock resistant, though I've found mine scratches a little easier than the headlamp material. At least it can be replaced for less money - I think this stuff is going for around $50 these days for both headlamps. It's thicker than the product they apply to the front of the car body.
 
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