Light Emitting Diodes (LEDs) have seen more and more usage in cars over the last few years. Most noticeably as those wacky “eyebrow” lights on Audis, but also in taillights, directionals, and running lights.
The advantages over traditional incandescent bulbs are numerous; they use less wattage, are brighter, and produce that cool no-transition effect of being flicking on and off instantly. They don’t generate nearly as much heat in the front as incandescents either. However, they do get very hot at the resistor behind the bulb. It’s not too much of a problem for brake lights and occasional-use lights, but it presents a design challenge for the bigger-sized LEDs that need to run constantly light headlights and taillights.
This is why you should be careful when swapping your taillights with LED from AutoZone, or trying to make your own LED headlights (these are starting to emerge in the aftermarket, but still aren’t available for many applications. They might look sweet for a couple hours, but if the housing isn’t meant for dissipating the resistor’s heat properly
Engineers at Lexus, Audi and even Cadillac have employed LEDs for the biggest lights on their cars… but they’ve spent a long time researching how to set them up so as not to melt the rear housing of their lighting modules. Apparently the new Escalade ESV was the first American car to ship with full LED headlamps… although I have yet to see one on the road.
Keep watching the market for LED innovations… once the technology improves they may surpass HIDs as the performance lighting item of choice.