QuestionWhy do headlights get milky with age? Seems like a lot of cars from the late 90's and early 2000's have this problem. Was it one manufacturer? Is there something other than replacing the whole headlight that can be done . I've tried cleaners, but it seems like the plastic lense is just eroding? Was there ever a recall on these? I have a 2001 Olds Silouette.
Answer The headlights you are referring to are called "composite" headlights. The composite part is plastic. A little history is in order. When headlights were first fitted to cars, they were basically candles with lens in front. Then, because brighter lights were needed to accommodate the higher speeds of the newer cars, they came out with acetylene headlamps. There was a little acetylene generator in the lamp or sometimes on the running board, and the gas was burned behind a lens. It was a very bright and very dangerous solution. Then they developed electric headlamps, with separate bulbs. Eventually these grew into "sealed beam" headlamps. Then the government stepped in and required sealed beam headlamps of certain sizes and brightness; no other types allowed in the U.S. This is why you will see European versions of Mercedes or Jaguar with different lamps than the U.S. versions. Finally, in the interest of promoting aerodynamics, the U.S. allowed manufacturers to fit headlamps of their own design to their cars. They still had to meet certain brightness and beam-shape criteria, but they could look cool and streamline the shape of the front end. American manufacturers made these lamps almost exclusively from polycarbonate plastic (Mercedes stuck to glass, and you won't see a faded lens on one of those cars). It is tough, strong, and shatter-resistant and can be molded into any suitable shape. It also has excellent optical characteristics. One thing they didn't consider, and which didn't become evident until many years into the program, was that the plastic was vulnerable to ultraviolet radiation. The more time a car spends out in the sun, the faster the lens deteriorates. Good news is that the deterioration is only the outside few layers of molecules. But, it is very hard plastic and can be tough to resurface. I have had good luck with the system sold by Mother's Polish; you need a drill to spin the little tool that they give you, but it works pretty well. Rock Auto, an online parts vendor, has an inexpensive replacement headlamp assembly available for $30.89 ea., which might make simple replacement sound attractive. Keep the old ones, polish them when you have a chance, and you'll have a replacement in case one is damaged in an accident.
There is another problem you will see with these headlamps, and that is when the seal between the lens and the reflector goes bad. Moisture will get inside and fog the inside of the lens as well as the reflector. This can usually be cured with a hairdryer aimed through the hole the bulb goes in, and some silicone to seal around the joint. Again, those replacement lamps sound attractively inexpensive.
