Problems with xenon systems and their causes
Second guest article by Carsten Aring, responsible for Light Technology in Hella’s Technical Service division.

A man who knows all the ins and outs of xenon headlamps: Carsten Aring, auto shop specialist at Hella.

According to the failure statistics, issues with electronic control gear or ECGs, as they are known, are the second most frequent problem, closely following worn lamps. ECGs are the central components of headlamps, controlling all physical values (current, voltage, frequency, etc.) required for the operation of xenon lamps. Temperature fluctuations, moisture, voltage peaks, vibrations and so on are among the main failure criteria. Diagnosing faults and exchanging ECGs is a job for an expert.

Electronic control gear from Osram (photo) or Hella rarely cause problems.

After all, these tasks not only call for specialist knowledge but also for a diagnostic tester. This is hardly the kind of gadget one is likely to have lying around in the garage.

In his next article, Carsten Aring will be looking at damage to headlamp lenses.

Carsten Aring has worked for Hella since 1998. The motor vehicle mechanics master craftsman and state-certified technician is responsible for the Light Technology department in the commercial sector of the Technical Services division. Apart from training and overseeing Hella employees, he also compiles the associated technical documentation.

Problems with xenon systems and their causes
A guest article by Carsten Airing, responsible for Light Technology at Hella’s Technical Service division.

Auto shops call him when a problem with xenon headlamps leaves them baffled: Carsten Aring, auto shop specialist at Hella.

Xenon headlamps have been around for 20-odd years now. Initially confined to top-of-the-range vehicles, xenon systems have since found their way into nearly all vehicle classes. A range of different xenon systems are currently used to cater to carmakers’ increasing demands and to keep pace with technical advancement. The light functions, too, now extend far beyond the generally known low-beam and high-beam light. Modern xenon headlamps can produce up to eight different light distributions. Depending on the driving situation and weather conditions, this ensures the best possible visibility for the driver.

But even in a high-tech system such as this, the light source – the xenon lamp – is still a wearing part that eventually needs replacing. However, with a service life of up to 2,500 hours, the frequency of lamp changes is minimal, generally being required only once during the lifetime of the car. Nonetheless, this is still the main reason why headlamps stop working. In such an event, it is highly inadvisable to tinker around with the headlamp oneself, as a perilously high voltage of over 30,000 volts is required to make the xenon lamp shine. What’s more, changing the lamp unprofessionally may cause irreparable and expensive damage to parts. For instance, if excessive force is applied when mounting the plug connectors, the lamp base or the ceramic tube of the return pole may be damaged.

Xenon lamp destroyed due to unprofessional change

My top tip: Xenon lamps should only be changed by a professional. 

The next guest article addresses problems with electronic control gear and other potential faults affecting xenon light.

Carsten Aring has worked for Hella since 1998. The motor vehicle mechanics master craftsman and state-certified technician is responsible for the Light Technology department in the commercial sector of the Technical Services division. Apart from training and overseeing Hella employees, he also compiles the associated technical documentation.

From the numerous emails, and when reading through the forums, we sometimes get the impression here at the carlightblog that xenon light is a failure-prone technology. Drivers complain of flickering headlights, headlamp range controls that don’t work and even of poor light. Now, we are sure that xenon not only emits plenty of light, but also that it needs less maintenance than halogen. The lamps simply last considerably longer.

But the end of the service life is not abrupt, like it is with halogen lamps or LEDs. With xenon, you don’t have a filament that burns out. It is more comparable to fluorescent tubes: pending failure is signaled by multiple ignition attempts. In other words, the light flickers. Unfortunately, there are also other causes for this bothersome phenomenon.

The most common source of problems with xenon light is – like with halogen – the lamp it-self. Normally the lamp only needs to be replaced once in a car’s lifetime.

Taking a closer look at other complaints about problems with xenon light shows that the technology is not usually to blame! The wrong lamps, or lamps from dubious sources, were installed, or someone has tinkered unprofessionally with the headlamps, which is a pretty intrepid undertaking considering the high voltage they carry. In these cases, you shouldn’t be surprised if the headlamps on a car over ten years old show a few signs of infirmity.

The complaints about poor light are confusing at first, especially since the lamps in question have the highest output of them all. But this puzzle is easily solved most of the time: these dissatisfied consumers looked right in front of the car, or even stood right in front of it to judge the light. This is not the way to evaluate the light on any car. What are most important are the points at a greater distance from the vehicle, for example on the right-hand side of the road between 50 and 75 meters away. And more blue does not mean more light.

Other tales of woe are not so easy to explain away. We got advice from someone who knows xenon technology like the back of his hand: Carsten Aring is responsible for Service and Support for auto shops at headlamp manufacturer Hella. Starting this week, he will be contributing a series of articles to carlightblog on the most common problems encountered with xenon light.

This car sets the standard for the state of the art: The E class from Mercedes has premiered a number of innovative systems and features over the last few decades, and is about to do so again. The new model coming out of Stuttgart is delivered exclusively with light-emitting diodes in the low beams. A full LED headlamp with additional functions is available as an option, and even its high beam light is provided by semi-conductors.

The standard version of the BR212 (Daimler’s in-house name for the car) is equipped with a headlamp that uses an LED module to generate the low beam light. Light-emitting diodes also supply the daytime running light. When these are dimmed, they serve as park or position lights. The high beam light comes from an H7 halogen lamp and the blinker is an orange incandescent lamp.

The full LED headlamp really jacks up the luminous flux. According to critical light experts, it not only stands up to xenon light, it also offers several additional light functions, such as glare-free high beam light and different light distribution patterns for country roads and highways. The main light is generated by a VarioLED module from Hella, the manufacturer of both headlamp types. The design of the module is similar to that of BiXenon headlamps. A drum produces the different light distribution patterns. This sets the Mercedes headlamp apart from LED models made by other manufacturers, in which the individual light-emitting diode modules are switched on and off to achieve the different light distributions. The advantage of VarioLED technology is its very homogeneous light. Its uniform appearance is highly reminiscent of xenon, which is not always the case with matrix systems.

Osram supplies its Ostar and Oslon LED modules for the top-of-the-line headlamps in the new E class.

The light sources in the headlamp are from Osram. It incorporates two modules each with six Ostar and Oslon light-emitting diodes. Incidentally, these can be replaced if one should fail, although that is highly unlikely because the service life of the LEDs is longer than that of the car.

The new Mercedes has a static cornering light integrated in the main headlamp, which does not make use of a combined bend and fog light. It comes from an LED light source just like the daytime running lights. The latter use optical fibers, a technology that currently is on the rise. This same module is dimmed for use as a position light.

Fogged up headlamps, Part 3: The severe cases

Modern headlamps have a very practical ventilation system that largely should prevent fogging. And it does for a long time, until suddenly the headlamps start fogging up more and more. What can you do then? Maybe one of the vents is clogged. The top ones usually are easy to reach, so you can inspect and clean them if necessary. In some car makes there is a piece of foam inside the vents, which you can also clean. Quite often insects find their way into these openings as well. The bottom air inlets make cleaning difficult. Cotton swabs do a good job if you can reach them without dismantling the headlamp.

Cleaning the vents on the headlamps can do wonders for preventing fogging.

Unfortunately some really severe cases of fogging do occur. In these instances, the engineers have slipped up and the ventilation system works only in a dry desert climate. In some cases, shame-faced engineers have come up with some strange service solutions, including rubber hoses that are connected to the vents and allow the headlamps to draw air from dry spots in the engine compartment. Just ask at your dealership and you may get some surprising answers that really work sometimes.

Then there is real damage, of course, that allows water to get inside. Cracks in the lens are an example. The only solution in this case usually is to replace the part, and that means replacing the entire headlamp in most newer cars. In older cars and particularly those with lenses made of glass, it is possible in most cases to repair the damage. A lot of times you can even purchase a seal individually as a spare part. It can help to repair the not-so-uncommon leaks that develop between the lens and the headlamp housing. If some kind of bonding is required here, good butyl tape can help, like that used to mount windshields. For a quick and dirty solution, you can even try chewing gum.

Have problems with fogged up headlamps or lights? Tell us about your experiences and let us know if our tips were a help, or if you still have any unanswered questions.