I found a partial solution to foggy headlamps since replacement headlamps are at least $100 each for imported salt water salvage parts.
Get a spray bottle of bug spray with DEET in it. Can be found at Bass Pro, Cabelas, Gander Mountain or any outdoor store. Spray it on the lens and wipe it off with a paper towel. It does not make them look like brand new but it does a great job for ten dollars.
Keep in mind that they will yellow again since the UV coating is already worn off.
Hmm. Yet another solution to add to commercial products (e.g., Maguiar’s), toothpaste, and I don’t know what-all else.
You mention yellowing. I have not noticed yellowing on my '04 Camry with about 100K. Rather, my problem was/is micro scuffing (from road grit, I presume) that has to be polished out. Does your idea work for that?
And be sure not to accidentally get any of the spray on the body of the car since it will eat the paint off of it.
And the headlamps will be just as cloudy again in a few months.
My wife used toothpaste on her car & it made a big difference . I bought one of the kits that has all the stuff in it to do the job but haven’t got around to using it yet . I read that after using something to clean the lens , keeping them waxed would keep them from yellowing again .
You can buy the uv spray to recoat them. I have polished my own sets with progressively finer sand paper. I start with 600 and finish with 2000, using a hose on low to keep the paper clean. I finish with a polishing wheel in a drill. When done the headlamps look almost new.
I tried bug spray, it worked OK. Not clear as new but not too bad. It didn’t last very long.
Try this,
It works… 9 months so far
I can second the recommendation for the headlight restoration kits. If you use them right, they work very well.
I usually use the kit’s materials, but I do it by hand. I’ve found doing it with a drill like they tell you to tends to result in the drill bouncing along the headlight and you end up with an uneven polish. Doing it by hand takes longer, but the results are excellent.
Another thing I do is to make sure to wax the headlight whenever I wax the car. This keeps it from yellowing again.
I’ve used headlight restoration kits, and they work.
I’ve also used polishing compound and that works too.
Any viscous media with micron-sized abrasives suspended in it will work great. One trick I use is to use a well wetted sponge polishing pad in an electric drill. It does a fantastic job. Be sure to tape off the painted areas around the lighting module before proceeding. Anything that will clear the lens surface also has the potential to quickly damage the paint.
I too wax the surface after I’m through. Seems to help.
Get a spray bottle of bug spray with DEET in it. Can be found at Bass Pro, Cabelas, Gander Mountain or any outdoor store. Spray it on the lens and wipe it off with a paper towel. It does not make them look like brand new but it does a great job for ten dollars.
And for a couple bucks more you can get products that were designed for this and results that look better and last longer.
I’ve used the restoration kits and the best I’ve gotten out of them is about two years. I had my local body shop sand and clear coat the lenses on my Sienna and, after one year, they still look almost new.
I have used the 3M kit and been happy with the results, but it wasn’t untiI I installed brand new non-OEM headlights from Rock Auto for less than $100 each that my 1999 Honda not only looked close to brand new up front, the night time vision was dramatically better.
Headlamp lenses deteriorate over time, both inside and out. Whatever you do to repair the outside, the results are nowhere near brand new in terms of performance (safety) and life expectancy.
New After-Market Replacement Headlights For Certain Makes/Models Aren’t All That Expensive. I Believe Headlights For My Grand Prix Can Be Purchased For Less Than $45 Each , When Purchased As A Pair, And Include Free Shipping.
It takes ten minutes to install them. Even if quality isn’t up to the of OE, it makes one wonder if screwing around with a $15 restoration kit is worth it.
CSA
I bought the replacements online and they even came with bulbs. They have started to yellow after 5 years. The OEMs last longer, but the cheap ones you can replace 5 times for the price of one set of Toyo OEMs.
Whatever you do to repair the outside, the results are nowhere near brand new in terms of performance (safety) and life expectancy.
I respectfully disagree. If you do the job well enough, the results are close to if not exactly like the headlights were when new. All the headlight lenses are is a chunk of clear plastic that’s been polished very well, which is exactly what you’re doing with the restoration kits.
What I have found, however, is that if you do what the kits tell you to do, you won’t get perfect results. The sanding parts should be done without the drill because the drill will leave swirls in the plastic. Wetsanding with straight strokes rather than spinning on a drill will produce better results.
I have recently been doing some research on adding a clear tint film to the headlight before it goes south. There are pre-cut films that are relatively expensive, but for $6-7 you can get a roll of film and then stretch/cut/fit to your headlight. I will continue my research before shelling money and time.
I may have made too general a statement, shadowfax. I put new headlamps on my 1999 Honda less than a year ago. The results were dramatically better than the good-looking results of using the 3M polishing kit… but, in my case I was replacing 15 year old repaired lenses with brand new.
Galant, I would wonder how heat affects the film. It reminds me of the wide thick clear tape we used to put on customers’ new skis. For cars it would have to be more stretchy, and have excellent UV protection as well as resistance to abrasion from airborne particles. Please let us know what you find out.
I respectfully disagree. If you do the job well enough, the results are close to if not exactly like the headlights were when new. All the headlight lenses are is a chunk of clear plastic that's been polished very well, which is exactly what you're doing with the restoration kits
That’s not true. OEM lenses actually have a UV coating or cap layer that is bonded to the polycarbonate base material. This is the layer you’re sanding/polishing away to restore the lens. Professional restoration kits have a UV coating as a final step that can be re-applied and cured with intense UV light to provide an almost like new restoration. Almost but not quite. Can’t really beat that OEM thermally bonded cap layer…
“clear tint”…hmmm…have to think about that one…
Okay, clear bra; get it 
Those old Honda headlights were famous for getting compromised and deteriorating from the inside as well as the outside. It happened to my 1999 Accord. My 2004 Sienna has no signs of interior degradation so the restoration to the outside done by the body ship (with a clear coat) has made them look like brand new lenses. After a year they still look new so we will see if the professional clear coat lasts longer than the Sylvania kit (highly rated by Consumer Reports). The Sylvania kit lasted about two years before fogging over.