Cleaning yellow film off headlights

[dr_nelson]

As HDR mentioned, I did this myself for the cost of some fine grit sandpaper and some Rustoleum 2x clear coat spray.
(...)

I did the same thing. Works like a charm.

1. 400 grit sandpaper.
2. 600 grit sandpaper.
3. 2000 grit sandpaper.
4. clear coat spray.

The only challenge was to find 2000 grid sandpaper. It will look really foggy after sanding it, but after putting the clear coat on, it looked like brand new and totally clear (and I have yet to see it turn foggy or yellow again - that was 2 years ago, and that car is never parked in a garage).
To see whether it is OK to put on the clear coat, just put some denatured alcohol over it and it will shine absolutely clear for a few seconds.

 

[Vanada]

I thought about getting the 3M kit but was able to get all the single sheets of sandpaper I needed for about 1/3 the price by ordering it from Napa. That was 600, 1000, 1500 and 2500 (not 2000 as in my previous post). Total cost = $6 USD plus $4 for a can of clear coat from Home Depot. Canadian Tire stock 3000 I think but only in packs. 

Or there's this assortment:
https://www.napaonline.com/en/p/MMM03006

 

[TMG51]

Yes, get 2000 grit and up from any auto store, or the auto section in a hardware store. Not the regular sandpaper section in a hardware store.

 

[dextours]

I use any automotive CLEANING wax (contains abrasives) wipe on wipe off repeat until clear. You don't have to get it perfect the first try, just come back to it another time. Once it's clear, apply a protectant like meguairs headlight protectant or 303 aerospace protectant

 

[Spaceman Spiff]

For you cheap bastards (like me ):

Toothpaste is equivalent to 800 - 1200 grit sandpaper, depending on brand (7 - 15 µm abrasive diameter).
Baking soda is equivalent to 1200 grit sandpaper (~ 8 µm).

Any UV reflecting or absorbing coating will keep the lense from re-fogging as long as it remains on the lense.

 -- Spiff