Up until recently i thought the sun was the major reason for the headlights turning yellow.
But today when i went to buy the materials needed to try to clean the headlights the pep boys guy there told me i was completely wrong. He said the cause is from the bulb in the inside of the headlights. He also said that the only way to clean it is from the inside and not the outside.
man thanx i needed that...yes it is caused from the outside..actually the lens is cleaner on the inside than the outside..clean off the outside lens..and if you really ARE hardcore about it take apart the lens from the headlight housing and scrape the old glue out and re-seal it with clear silicone..looks like new...
hes way ahead of you, mikey alex, you should have slapped that pep boys fool like a dirty whore. dont listen to any pep boys, autozone, etc. employees, most of them dont know their *** from a hole in the ground.
In this forum, go to the Sylvania Xtra Vision thread. There are some suggestions there on how to clean your lenses. Ulta violet light is the culprit as well as poor maintance. They need to be cleaned and waxed on a regular basis just the same as your car.
It has been my experience, I could be wrong though, that the reason the headlamp covers turn yellow is not keeping them clean. The heat from the lamps seems to bake the grime into the lense. My wifes car had the plastic lenses, one replaced due to accident and the other could not be cleaned to matched. Body shop told me this.