in which I replace the headlight lenses on my car

or why it’s not worthwhile to resurface old headlight lenses
or ignoring the above, the right way to resurface, seal, and protect old headlight lenses

My 2003 BMW E46 330i is just a few months shy of hitting 14 years from its build date.

The years that I’ve had her have not been kind. They’ve often involved long periods of baking under relentless sun, haphazard upkeep, and infrequent washes.

For the first three years, she spent almost every second of every day outside in the Oklahoma sun. She spent half of her summers sunbathing in Houston, Texas. In the winter, I’d take her out on Tulsa’s salted roads. I relished snow days, where I could shred fresh-fallen powder and kick the rear tires loose.

Conditions remained this way while I attended graduate studies at the University of Missouri. The apartment complex that I was living in had no covered parking available, and she endured hail strikes on at least three occasions in that time.

So when I moved back to Houston in the spring of 2013, one of the things that I did was to ensure that she could spend some of her remaining days within the comfort and safety of a garage. By then, the damage had already been done.

While I was working car sales, I decided to patronize the detailer that we had on the lot. His name was Abraham, and he was a Mexican guy that mostly did touchup work on the used cars before they were listed for sale. On request, he would also perform work on personal vehicles. Abraham didn’t have access to the best equipment or facilities, and it showed (holograms aplenty), but I decided to go for it.

I can’t remember how, exactly, but Abraham talked me into letting him resurface my headlight lenses the one time that I asked him to help touch up the various battle scars on my car. The lenses looked good for a while, but their condition deteriorated at some point, and now they look horrendous.

I purchased new lenses (63126924045: Amazon.com, 63126924046: Amazon.com) from RMEuropean.com, selecting those manufactured by Automotive Lighting (AL). I also purchased new headlight cover strips (63126921859: Amazon.com, 63126921860: Amazon.com) from ECSTuning.com.

A little history: AL was established as a 50/50 JV between Magneti-Marelli and Bosch. In the year 2003, Magneti-Marelli took full ownership of AL. Small wonder, then, that my new headlight lenses arrived in boxes proudly bearing the Magneti-Marelli logo.

I had just finished installing the Mishimoto silicone air intake boot kit, and decided that I’d take a moment to swap out the driver’s side headlight lens. The new headlight lens was infinitely clearer.

New headlight lens
New headlight lens – note the clarity of the projectors as well as the reflections

When held next to the old lens, I could see the degree to which the original equipment had yellowed.

Old headlight lens
Old headlight lens, scarred by years of wear and tear

I turned on the xenon headlights, and was surprised by the difference in clarity and color rendition. The driver’s side light output was tack sharp and bright white, whereas the passenger’s side was dull and yellow in hue.

Comparison shot of light output between new and old headlight lenses
The difference in light output between the new lens (left) and the old lens (right) is evident

I quickly moved to replace the passenger’s side headlight lens as well. The car’s front end appearance is remarkably improved. Talk about eyes being the windows to the soul…

There are inherent risks involved in replacing the headlight lenses on any vehicle. On the E46 sedan, there’s a painted trim piece that goes beneath the headlight assembly. The old plastic tabs may crack during removal, especially when done without the use of trim removal tools.

Why do headlight lenses degrade?

Mechanical and/or chemical failure of UV-protective coating resulting in direct exposure of polycarbonate to the elements. Polycarbonate has low scratch resistance and is susceptible to UV degradation, which takes the form of yellowing.

What’s wrong with plain resurfacing of polycarbonate headlight lenses?

By polishing the lenses, one removes the original UV-resistant coating. Unless this coating is replaced, the results can be expected to fade rapidly.

What are qualities to look for in a coating for headlight lenses?

The ideal coating to apply after resurfacing a lens would be clear, protect the polycarbonate from UV exposure, form a strong bond with the polycarbonate surface, and have wear resistance. I’ve identified the following products through my own research:

Coatings suitable for polycarbonate headlight lenses

Dupli-Color Headlight Restoration Kit – Clear Coat Step 2 5 oz – HLR300 ($14.99 kit, Amazon.com)
Krylon UV-Resistant Clear Coating, Clear Gloss, 11.0 oz – 1305 (~$12, Amazon.com)
(both Dupli-Color and Krylon are owned by Sherwin-Williams)
Solaray UV Clearcoat – 12 oz (~$40, Amazon.com)

Ideal protection for headlight lenses would include a clear vinyl appliqué. Lamin-X is the leading brand name in this department. They offer precut films for a wide variety of vehicles.

I applied Lamin-x B011CL (BMW E46 Sedan fitment, Amazon.com) to my new lenses to ensure that they will hold up through the years to come.