Hi,
I'm thinking about getting a 2014-2016 e350 with full LED. The question I have is since I'm getting a used car, does the quality of light in the LED degrade after a few years? (e.g. I've seen HIDs on older cars that are as bright as halogens on newer cars) And if so, has anyone had to replace the LEDs? How expensive are they?

 

Generally, this is something so miniscule that you shouldn't worry about it. But here is some thought...

LEDs theoretically do degrade over time, mainly due to the components overheating which creates stress on the component. Keep in mind, LEDs are mini diodes, they are fairly basic components with no moving parts, like a capacitor. They rarely fail. However, they can age if they overheat. In very rare cases, they can fail if they overheat.

Considering the headlamp should have numerous heat sinks to reduce excessive heat, the LED headlamp shouldn't have any major issues. But it is difficult to be certain. Furthermore, LEDs are usually turned on at night, the coolest part of the day.

Generally, LEDs shouldn't have major degradation throughout the life of the vehicle. But here are some things that would likely cause LED degradation:
1. The car's headlamps are on during the day (some drivers turn the lights on for safety). This may have a major effect; the heat from the LED and the heat from the day in a warm climate could cause the diode to experience more wear.
2. The car's headlamps are cycled on and off repeatedly, this may have a small minor effect.
3. Cars that live in hot weather (Las Vegas, Arizona, New Mexico, Texas, MS, Alabama, Florida, things of that like). The higher heat can potentially cause the LED to degrade more and faster.
4. An LED with a design that doesn't have enough cooling capacity. Not enough heat sinks, or too hot of a design without enough cooling can reduce the brightness of the LEDs over time.


The Full LED headlamp probably costs somewhere around $2K to $3K per headlamp per side. So a pair of headlamps probably costs $4K to $6K. These are very approximate prices and dealers mark up tremendously sometimes. A typical Xenon headlamp from Mercedes is around $2K. Headlamps are very expensive parts. Insurance companies hate them because they're often some of the most expensive things damaged in a small accident.

 

 

That's good to know! And thank you for the detailed information that they continue to run even when the car is shut down! That's fairly clever of them to do that!

 

Just a small add to the good information posted by @patrick_y:

- Nowadays the prices of Led headlamps are not so high anymore.
For 1100€ you can buy a brand new LED Headlamp from Hella.

Ex: Hella Led

But yes... still expensive as hell :-)

 

My 14 headlamps are doing fine too. HIDs tend to fade over time because it's really still a single bulb attached to a ballast. LEDs have a bajillion diodes and produce way less heat as well. Our headlamps new from dealer around about $3300 each side.

 

HID xenon bulbs fade over time due to the chemistry behind how they produce light. They vaporize metallic salts that produce the amazing bright light, however there is only a finite amount of this metallic salt in the bulb, and once it's gone, it's gone. Now, LED bulbs work on a completely different principle. They do not make use of, or rely on any chemical to produce light. They create light on a completely different solid state principle that doesn't use up any materials, and in theory could last forever (if treated right) without loosing a single lumen of light. However, due to certain inescapable inefficiencies (such as the heat-cool-heat cycle) the LED will eventually fail, but it will never lose any power. It will either work or it won't, there is no inbetween. The expected lifetime of a single LED diode is around 50,000 hours. Compare that to the average lifespan of a HID xenon bulb of about 2,000 hours. As you can see, the expected lifespan of an LED diode is well in excess of the lifetime of the car. And the Mercedes-Benz LED headlights have many LED diodes inside. The LED headlight technology is far superior to the HID technology in every way conceivable. This is why the LED headlight is the future.