# FAQ - Shedding Some Light on Halogen Bulbs, Xenons and LEDs



## SwissJetPilot (Apr 27, 2014)

For those of you who many not be familiar with the name *Daniel Stern* , he is an automotive headlight expert out of Vancouver, British Columbia, Canada. In this discussion he was kind enough to share his expertise on the topic of the best *Halogen bulbs* for Mk2 TT headlights and some of the issues regarding the performance of these bulbs. In addition, we also touched on the subject of *Xenon* bulbs and also his opinion on the popular trend of swapping OEM bulbs for *LEDs*.

Update - For anyone interested in the topic of fog lights, I have added another great post thanks to Daniel discussing *Selective Yellow Light* which can be found *here*.

Thanks again to Daniel for sharing this information with the Forum. It's a bit of a long read, so get yourself a cuppa, sit back and enjoy.

*Halogen Bulbs - *

Two of the over looked factors in poor halogen headlight quality can be attributed directly to the condition of the outer lens and reflector degradation. Regardless of which brand of halogen bulb you go with, if the lens or reflector isn't as clear or reflective as it was when it was new, the output of "brighter" bulbs simply can't over come these defects. You can read about polishing the outer lens in a post *here*.

*SwissJetPilot* -
One of the topics that comes up a lot (especially in winter) is the complaint about the poor lighting quality of halogen lights for the Audi Mk2 TT. Any comments or recommendations?

*Daniel Stern -* 
That's a legitimate complaint. The lamps are small, which limits the amount of light they can collect and the degree to which they can amplify it. Moreover, they're subject to several kinds of degradation. Plastic lens opacification (haze) is the obvious one. And lenses aren't the only part of the headlamp that degrades with age. The reflectors are shiny by dint of a very thin layer of vapour-deposited aluminium with a very thin protective clear topcoat. The topcoat eventually breaks down and allows the aluminium to begin oxidizing. Optical degradation of the reflector is severely advanced well before you could possibly see it with the naked eye; by the time the reflector has visibly degraded enough to be described as just a little imperfect, the lamp is past dead 

Nutshell version: this is not like trying out different bulbs in the kitchen or living room or garage, where all it has to do is light up in a way we find adequate and pleasing. Headlamps aren't just flood or spot lights; even the cheapest, most minimal headlamp is a precision optical instrument. They have a complex, difficult job to do in terms of simultaneously putting light where it's needed, keeping it away from where it's harmful, and controlling the amounts of light at numerous locations within the beam to appropriate levels (too much light in certain areas is just as dangerous as not enough). 

Headlamps cannot just spray out a random blob of light, and that's what they do with anything other than the intended correct kind of light source even if "but the cutoff is still apparent!".

For the halogen lamps, the stock bulbs are a long-life type as automakers like these because it keeps people from demanding new bulbs under the new-vehicle warranty, but that's about their only advantage. The filament configuration required to make a long-life bulb tends to reduce the output, luminance and beam focus, which shortens seeing distance and makes the light browner. The opposite filament changes are made to create high-luminance bulbs: lifespan is shorter, but luminance and output are higher and the beam focus is better so seeing distance is longer and beam coverage is wider. Light color is whiter and less brown. And the lifespan difference is less stark than it might seem, because the long-life bulbs not only start out dimmer, but they last (i.e., keep lighting up) long enough to lose significant amounts of their original output. The higher-performing bulbs burn out before they drop much of any intensity.

The attached page (click *here*) from a Hella technical paper goes into some detail on the performance difference between a standard bulb and a higher-luminance bulb. When it was written in 1997, the state of the art was young, so this is a comparison between a new standard bulb and a new "+30" bulb with modestly increased luminance. The difference is bigger when comparing old long-life/low-luminance bulbs, and even bigger still because additional research and development has brought us to the present where we have even better high-luminance bulbs.

So yeah, bulb selection matters a lot to how well you can (or can't) see at night. Please see bulb test results posted by my colleague Virgil over at *Candle Power Forums* and note the performance difference, especially on low beam, between the standard-wattage, standard-luminance bulb "A" and the standard-wattage, high-luminance (or "high efficacy") bulb "C".

Now, particulars: the Audi TT Mk2 (8J) '07-on uses two H7 bulbs per side of the car, one for dip (low) and one for main (high) beam. The '06-down cars use H7 only for main beam. If you want to be 100 per cent squeaky legal, fit the best 55-watt H7 bulbs you can get—that'll be the likes of the Tungrsam Megalight +120, the Philips Xtreme Vision, or the Osram Night Breaker Unlimited - and see to it you never, ever exceed the posted speed limit. Also make sure to floss your teeth twice a day.

Starting in about 2003, the very best H7 was an item made by Osram: a 65-watt item producing 2100 lumens (versus the standard 55w H7 bulb's 1410 lumens, or a high-performance 55w H7 producing about 1550). The extra 10w was not enough of an increase to pose hazards to the circuitry or the lamps. Osram stopped making that bulb in 2017 or so, and instead started selling an 80-watt item inferior in every respect: much higher current draw makes it incompatible with most cars' wiring, its lifespan is much shorter, beam focus is poorer on account of the larger filament, and (punchline) it puts out less light! In response, I set to work to arrange for new German production of a bulb identical to the 65w item. That work bore fruit, and I keep them in stock (click *here*). I'm not saying if you put these in, you can exceed the speed limit or skip down to just one flossing per day. The low beam bulb on the '06-down cars is an H1. Tungsram Megalight +120 is the pick of the bunch here.

"But wait, what about the Tungsram Megalight +130 or +150? The Osram Night Breaker Laser? The Philips GT200? Surely those are better, right?" 

The number after the plus is bigger, so - Yes, it is. But no, they're not. They have more and deeper blue tint on a greater area of the bulb capsule, and that's to the detriment of the driver trying to see at night. The high-plus-number bulbs do have an untinted band near the filament, so okay, that's somewhat better, but less blue tint on the glass is always better than more. It's really that simple: any amount of blue filtration sharply reduces the amount of light reaching the road in exchange for no benefit at all except a bogus appeal to fashion. Headlamps are life-safety equipment, not fashion toys, so this is a bad deal and those bulbs are best avoided.

And to finish that topic: any of the bulbs claiming to produce "extra white" light (or super white, hyper white, platinum white, metal white,Xenon white, particular colour temperature, etc) as its main "benefit" is best avoided. It doesn't matter whose name is on the bulb -- Sylvania SilverStar/Ultra or ZxE, Osram CoolBlue, Philips BlueVision or CrystalVision, Wagner TruView, anything from PIAA or Hoen,, Nokya, Polarg, etc. - all the same scam. The blue-tinted glass changes the light color a little, but blocks light that would reach the road if the glass weren't tinted, so they give you less light than ordinary bulbs (not more). 

To get legal-minimum levels of light through the blue glass, the filament has to be driven very hard so these bulbs have a very short lifespan, and there's nothing about the tinted light that improves your ability to see -- the opposite is true (less light = less seeing, no matter about the tint). Sylvania got spanked to the tune of thirty million(!) dollars for false and misleading "upgrade" claims for Silver Star bulbs (click *here*) and those are among the least-bad of an overall bad product category, so the maths kind of do themselves.

Now, what about the blue ring just below the tip of some of what I've classed as good bulbs, including the Tungsram +120 items? 

That's actually completely different. The marketers say this is there to make a fashion statement with your headlamps, but it's really there for a stealthier reason: to cut the mean spherical output of the bulb down to legal levels as tested in an integrating sphere (the machine used to measure light output from a bulb to determine if it falls within the legally required range). The blue ring filters a part of the bulb that has nothing to do with beam formation because it's not located between the filament and the reflector. So it cuts down on the total light output from the bulb when all directions are considered, as in the sphere, without reducing the light output in the relevant directions as in the headlamp. 

In other words, the filament is pumping mad lumens through the uncoloured glass where the reflector is looking. Clever trick. It works. But in H7, the 65w item completely wipes the floor with any others.

*SwissJetPilot - *
We often see chart and graphs from manufacturers and various Forums that discuss "brightness" as a key indicator of bulb performance. What's your take on this?

*Daniel Stern - *
"Brightness" is not an objective measure of anything; it's a subjective feeling just like loudness. Is some song by Metallica louder than, say, Bach's Brandenburg Concerto № 3? The average listener would say yes, even if they're played at the same sound pressure level (the objective quantification of how much sound there is). 

The facts are that the maximum possible output from a 55-watt, E-marked H7 bulb fed 13.2 volts is 1,650 lumens—no matter whose name is on it nor what claims might be made. The minimum possible output from the 65-watt H7 fed 13.2 volts is 1,890 lumens, and in practice they tend to run close to their nominal 2,100-lumen rating.

The high-output 55w H7s (Osram Night Breaker range, Philips X-treme Vision range, Tungsram Megalight range…) have a high-luminance filament. So does the H9 bulb, which is relevant because the 65w H7 bulb is an H9 burner (=glass capsule + filaments inside it) on an H7 base. So with the 65w H7 bulb you have high luminance as with a top-notch 55w bulb, and more light than you can get from a 55w bulb.

With that education out of the way, here are some objective, measured comparisons between H11 Long Life, H11 +100, some pathetic LED pretend-bulb, and H9 in a particular projector-type dipped beam: White wall & lux comparison: LED, H11 LL, H11+100, H9

H11 and H7 are closely comparable, differing primarily in base design; the burners aren't identical, but they're close, and all these bulbs we're talking about (H7-H9-H11) have common burner geometry, so this comparison is a sturdy basis for predicting the effect of putting the 65w H7 in place of a 55w H7. The light-above-the-cutoff concern doesn't really exist with the projectors in this test; the 65w bulbs increased it, but didn't push it beyond US limits in that region of the beam. And the projectors in the TT, both US- and rest-of-world varieties, have much tighter control over light above the cutoff than the Japanese projector used in the linked comparison.

*SwissJetPilot -*
What is the life expectancy of the 65-watt H7's?

*Daniel Stern - *
In context, here are B3/Tc lifespan figures at 13.2v for a variety of bulbs. B3 is the hour figure at which 3 per cent of the test bulbs have failed; Tc is the hour figure at which 63.2 per cent of the test bulbs have failed. These are standard life test points, and the values given here are from Osram's databook; other reputable(!) makers' bulbs are closely similar:

• Ultra Long Life H7: 1000/1500
• Long Life H7: 700/1200
• Standard H7: 330/550
• High luminance H7: 250/450 (e.g., Osram Night Breaker Silver)
• Highest luminance H7: 150/250 (e.g., Osram Night Breaker Laser)
• H9 (=65w H7): 250/500

Again, mind that the filament configuration required to make a long-life bulb tends to reduce the output, luminance and beam focus, which shortens seeing distance and makes the light browner. The opposite filament changes are made to create high-luminance bulbs: lifespan is shorter, but luminance and output are higher and the beam focus is better so seeing distance is longer and beam coverage is wider. Light color is whiter and less brown. And the lifespan difference is less stark than it might seem, because the long-life bulbs not only start out dimmer, but they last (i.e., keep lighting up) long enough to lose significant amounts of their original output. The higher performing bulbs burn out before they drop much of any intensity.

*SwissJetPilot - *
And what are your thoughts on LED or HID replacements for factory halogen bulbs?

*Daniel Stern - *
First principles: halogen lamps need to use halogen bulbs. The "LED bulbs" now flooding the market, claiming to convert halogen headlamps to LED, are not a legitimate, safe, effective, or legal product. No matter whose name is on them or what the vendor claims, these are a fraudulent scam. They are not capable of producing the right amounts of light, nor producing it in the right pattern for the lamp's optics to work.

More detail at -
https://jalopnik.com/why-most-led-headlight-upgrades-dont-really-work-an-ex-1843070472
To go along with the "HID kit" debunk at -
Daniel Stern Lighting Consultancy and Supply

*SwissJetPilot - *
A bit off topic from the subject of halogens, but do you know why yellow fog lights are banned in the EU?

*Daniel Stern -* 
They're not, they're just no longer popular. The trend now is bluer and bluer and bluer, with a bunch of marketeering nonsense behind it (blah blahbitty _closer to natural daylight_ blah blah no it's not).

*SwissJetPilot - *
In Switzerland yellow fog lights are still legal and I still see them occasionally in France, where the entire headlight is yellow. But generally it seems yellow fog lights are a thing of the past.

*Daniel Stern - *
Generally so. Still popular to some degree in Japan. It's no longer possible to get proper yellow bulbs in quality worth having, at least not through the front door. Along with those special H7s, I have availability of uncatalogued yellow bulbs in the various types (H3 for the '06-down TT fog lamp; H11 for '07-up).

That said: even very good fog lamps (which do exist, but aren't very common) are of almost no use to most drivers in most conditions. Fog lamps should spend almost all their time turned off. Please see this* link* for thorough information about what fog lamps will/won't and can/can't do.

*SwissJetPilot - *
Thanks again for taking the time to share your knowledge and expertise with our humble little forum. Hopefully others will find this helpful when it come time for them to replace their bulbs and are looking for replacement options.

*Daniel Stern - *
You're welcome.

If anyone has any additional questions or is interested in the products Daniel offers on his website, be sure to reach out and contact him directly at *Daniel Stern Lighting*.

*H7 Halogen Bulbs (65-watt, 2100-lumen) *









These single-filament bulbs are found in the low beams, high beams and fog lamps of many European and Japanese vehicles made since the 1990s. Fun Fact: The H7, introduced in 1993, was the first new halogen headlamp bulb design type-approved to Europe's Regulation 37 in twenty years. It touched off a wave of research and development that saw a dozen new halogen bulb types introduced over the next 15 years.

Ultra High Output (_Vosla_) H9 burner on H7 base, race and special-purpose:
*$28.76/ea *or *$24.45/ea* for 12+ at a time.

*Exact replacement for the Osram 64217*, which was discontinued several years ago. After a great deal of work, I have secured new availability of first-quality, German-made 65w - 2100 lumen H7 bulbs.

They are *in stock and now shipping*! *Send me an email* to buy them.

*SwissJetPilot* -
Do you have any experience with shipping to the UK or Europe with regards to what people can expect to pay for shipping?

*Daniel Stern - *
Yes—I've shipped these bulbs to a good mix of countries in Europe and even further afield (Australia, New Zealand, South Africa). They're small and don't weigh much, so the way to economise is to order as many as possible in one go, then divvy them up over there. Group buy, for example. Note the bulb price drops from $28.76/ea to $24.45/ea for 12 or more bought at the same time. 









Luminescence can only be increased by increasing the coiled filament temperature, whereby the rate of tungsten evaporation also increases. By reverse logic, this means that to achieve a long service life the luminance must be reduced. In order to obtain the same luminous flux in spite of a lower luminance, it follows that the surface area of the coiled filament, and therefore also the filament size, must be increased. The consequence is that the luminous intensity, and therefore also the beam range of the headlamps, is drastically reduced using this type of bulb. The chart above shows the effect of reduced luminance on light characteristics.


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## wsantos (Sep 7, 2020)

Great post SJP! I'd never heard of the guy until now. He seems to be a legend within the automotive lighting industry from I could gather online. It'd be nice to have those 65W bulbs he developed (Ultra High Output Vosla) more widely available or at least subjected to testing and comparison with a modern day H7 55W. 

Sent from my SM-G996B using Tapatalk


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## SwissJetPilot (Apr 27, 2014)

I found his name popping up on a number of VW, Audi, and BMW forums going back a few years. It seems these Volsa 65-watt bulbs are quite popular and on eBay they're often referred to as "off road" halogen bulbs. Since he's in Canada, I asked Daniel about shipping prices to the EU and UK and will post his reply.

FYI - *Volsa GmbH*. You can read more about them *here*.


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## wsantos (Sep 7, 2020)

One think cross my mind though, how did he get Vosla to agree to produce a custom bulb and make it only available through him considering the obvious gap in the market? 

Sent from my SM-G996B using Tapatalk


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## SwissJetPilot (Apr 27, 2014)

You could always email him and ask.


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## darrylmg (Oct 16, 2021)

Will you be changing your Xenon bulbs @SwissJetPilot ?
It sounds like Daniel is saying that an ageing Xenon causes issues which can lead to other problems (ballst)?
I've got Xenons, they seem ok, but I bet they're originals on my 2010 car.


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## SwissJetPilot (Apr 27, 2014)

*Xenon Bulbs -* 

*SwissJetPilot - *
I have the Xenon's in my 2007 which are really great. I've read they should be replaced now and then but I've never quite understood why they should be replaced if they still work.

*Daniel Stern -*
Five years' worth of average usage is a reasonable guideline. You'll want to replace those bulbs unless they have very low runtime on them. They'll keep lighting up, but less and less, and with a greater and greater workload on the costly ballast. Hit *www.powerbulbs.com* and you'll find the good ones at much lower than stealership prices. 

*SwissJetPilot - *
Are there any visual indication of degradation of the element?

*Daniel Stern - *
Yes: look at your nearest calendar and compare the year to that when the bulbs were last changed! With normal usage, at 15 years old you're about twice or triple past wise time to replace. When the bulbs get really badly degraded you can get severe colour shift (pinkish, usually) or they'll flicker, refuse to light on the first try, and otherwise like that—by that stage they're working hard at killing the ballast/igniter as well. 

Short of all that, the output drops gradually so you never really notice it…until you fit new bulbs, especially if you fit the upgrade bulbs previously mentioned. But if the lamps are seldom used and don't have much runtime on them, then they probably won't have dropped much output from new (though the modern upgrade bulbs would still provide an upgrade). 

@ *darrylmg* - TBO I'm on the fence on that one . 
While my Roadster is now over 15 years old, I almost never drive at night since it's really a weekend, holiday car and not a daily driver. Even with frequent tunnels here in Swissyland, I doubt I have them on for more than 6 hours a year. Since I don't have the auto-light-on feature, the Xenon's don't get cycled randomly when going through tunnels or under bridges. And as I have the Scandinavian setting coded, I'm running with the LED DRLs so again, the Xenon's are hardly used.

When I did the *LED DRL Upgrade* and the *Tail Light Ground Fault Repair*, I replace all of the factory bulbs in the headlight and tail light assemblies at one go as there were obvious signs of them "silvering" inside the bulbs due to their age. According to Daniel, this "silvering" is caused when tungsten boils off the hot filament and condenses out on the relatively cool glass wall, where it remains forever. Halogen bulbs don't do this

I did remove and inspect my *Xenon bulbs*, and so far they both look okay. But as Daniel suggested, low hours many not need to be changed, but even so, not doing so could cause problems with the ballast later on. I suspect replacing the ballasts won't be cheap!


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## darrylmg (Oct 16, 2021)

Maybe that's a question for Daniel. How to tell when light output is no longer adequate/ optimum/legal ?

_EDIT - see Daniel's comment above._


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## Wolvez (Jun 22, 2018)

darrylmg said:


> Maybe that's a question for Daniel. How to tell when light output is no longer adequate/ optimum/legal ?


There is a device that measure that.

The stupid internal wiring inside the headlight are designed to fail. All wire insulation on mine complately fail and flakes out. Also check the xenon bulb holder for brownish color that indicates overheating








.


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## SwissJetPilot (Apr 27, 2014)

That's some serious insulation failure. Can you post some sharper images? Would be very curious about what's been going on inside your headlight assembly.

Looking back at some of the pictures I took of the insides of my own Xenon headlights, I have the exact same brownish color as do many others who have posted internal Xenon headlamp pictures. I contacted Daniel Stern to comment on why that's there -

*Daniel Stern -*
The brown resin-looking material you're seeing the base coat applied to the reflector before it is reflectorised. The base coating process winds up putting some of the material on surfaces other than the inner bowl of the reflector.


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## SwissJetPilot (Apr 27, 2014)

*Replacing OEM Bulbs for LEDs - *

*SwissJetPilot - *
Audi provided an option in their software for Bi-Xenon headlights to allow replacement of the DRL OEM bulb with a LED. Using a OBDII diagnostic device; (e.g. Ross Tech's VCDS) owners can change the code to accept the LED without any issues. *Note*_ - for anyone interested in doing this click *here*._

With this one exception in mind, what's your position on swapping OEM bulbs for LEDs for turn indicators, side markers, rear lights, etc.?









*Daniel Stern - *
This is almost always not a good idea. Here's what to know about LED retrofit bulbs in vehicle signal lamps (brake lights, tail lights, parking lights, turn signals, DRLs, etc).

First, the quick nutshell version:

• Answer to "Will it work?" is a whole lot more complicated than is commonly understood.
• Fundamentally different kind of light source, so unlike with filament bulbs, physical fit doesn't guarantee optical compatibility/acceptable performance.
• Giant mountain of unsafe junk on the market, all fraudulently hyped as an upgrade.
• A few legitimate products that work passably in _some_ of the lamps they fit in; important to check the actual function carefully.
• Optical compatibility isn't the only issue; there's also electrical compatibility and thermal concerns.

Now here's the long, detailed version:

Let's start with how signal lamps (parking lamps, turn signals, side marker lights, brake lights, tail lights, reversing lamps) have to work. It's a lot more complicated than just "Yep, that lights up and looks good to me". Please take a look at this post, which I wrote years ago, in re someone who was very ambitiously making his own LED taillights for an old Dodge Dart:66 dart LED prototype working for now

This info applies no matter what kind of light source we're working with; I point you at it not because I think you should go to the trouble of the involved measurements I describe (that was more for his build-from-scratch project), but just so you get some idea of the complexity involved beyond "Yep, it lights up".

Bulb-type lamps (brake light, tail light, parking light, turn signal, side-markers, DRL, whatever) rely on a point source of light, a glowing filament, that radiates more or less equally in all directions—a sphere of light—collecting and distributing that light with optics in the lens and/or reflector. An LED or group of LEDs can't duplicate such a sphere of light at the required scale, so the light distribution from bulb-type lamps equipped with "LED bulbs" like this is often seriously damaged.

LED substitute bulbs from legitimate makers have been evolving toward usability, on a wending path. The many off-brand items _not_ from legitimate makers are a nonstarter.

The few legitimate LED bulbs that exist work well in _some_ of the lamps they fit in. In others, they work poorly. Their performance has to be carefully assessed in whatever particular lamp they're installed in, by comparing them side-by-side with the original incandescents as reasonably well described (in an accessible DIY manner) atHow to Evaluate Safety of LED Bulb Retrofits in Brake, Signal, Marker Lights.

And in still _other_ lamps, they don't work at all, because all the legitimate LED retrofit bulbs have only rear/side-facing emitters. That works in some lamps with a reflector bowl behind the bulb to gather and magnify the light, but there's a whole other kind of lamp that doesn't use (or doesn't only use) a reflector bowl. Instead, these lamps have Fresnel-type optics, the kind where the lens has a central magnifying area directly in line with the filament of the installed bulb, and spreader optics surrounding that magnifier. Often the magnifier is a round bullseye and the spreaders are a series of round prismatic rings surrounding the bullseye, but sometimes the magnifier is square or rectangular and the surrounding prisms are rectilinear. If there's no light directly out the front of the LED bulb, there will be minimal to zero output from the lamp.

Philips used to make some LED bulbs that did have significant frontward light, but they discontinued them and now they market two different product families, both of which are inferior to that first family. Which is unfortunate, but that's the world we live in.

There are the thermal issues with LED bulbs. Unlike with previous light sources (light and heat coincident out the front of the lamp), an LED puts out light from its front side and heat from its back side. The light goes forward, the heat goes back. As the LED heats up, its light output drops (it's called "droop"), so each LED must have an adequate heat sink to carry the heat away from the emitter and prevent it heating up high enough to drop the output low enough to put the lamp's output below the minimum requirement. LED vehicle lamps (designed and engineered as such) have to pass tests for output maintenance with prolonged operation, because that's a real-world situation (stuck in traffic with foot on the brake, tail/parking lights or DRLs operating for hours on end, etc). 

This is a challenging requirement for even legitimate LED lamps, and it's a really difficult challenge for such a thing as an LED bulb, because there's a very limited amount of space for any heat sinking, and all of it's going to be inside the lamp there with the heat-emitting LEDs—there's no way to use outside air to cool the LEDs unless you have a big honkin' rear housing on the LED bulb. There are some out there like this, and they create physical-fit problems (not enough room behind the lamp for the big honkin' housing) and other issues related to improper fit in the bulb hole.

Then there are electrical issues. There's a legal requirement that a turn signal bulb failure must markedly change the flash rate—much faster or much slower—so the driver will be alerted the failure (no such requirement for brake lights, though; fun, eh!). The outage-detection always works on bulb continuity and resistance, and in those terms LEDs behave very differently than filaments. So installing LED bulbs typically results in the turn signals flashing much faster than the legal requirement of 60 to 120 flashes per minute. In the best case (older vehicles with plug-in turn signal flashers) this can easily be remedied by installing an LED-compatible flasher; they're available for many but not all vehicles. 

Without that, the advertised fix is to install "load resisters" like these https://www.amazon.com/dp/B00P2D46N2/?tag=2402507-20 , one in each feed wire running to a retrofitted LED bulb. That often restores the correct flash rate, but now we've got to figure out where and how to mount resisters that run very hot, in a manner that won't have them burning or melting stuff or causing a fire hazard. Plus, we've compromised the insulation on the wires by piercing them, usually with notoriously problem-prone "Scotchlock" type taps, the fold-over-and-crunch type notorious for causing future giant headaches in the form of electrical problems. We've also disabled the outage indication. All of which kind of weighs against the idea of installing LED bulbs for better reliability.

We're not done with electrical incompatibilities, though; there are three more kinds to consider. First, while there's no legal requirement for outage indication for any function other than the turn signals, many vehicles have lamp-failure monitors that alert for the parking lights, tail lights, and brake lights; sometimes the DRLs as well. Even if everything lights up with retrofitted LED bulbs, often the outage monitor won't shut up about it. Sometimes the monitor can easily be defeated (if it's a simple bulb that can be yanked from the dashboard), sometimes not. And some vehicles, notably various Mercedes, Porsche, and other German models, tie the cruise control circuitry into the brake light circuit in more than just the usual simple "brake lights on = cancel cruise control until it's reactivated" manner everyone does. On such models, the cruise control will not engage if LED bulbs are installed.


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## Wolvez (Jun 22, 2018)

SwissJetPilot said:


> That's some serious insulation failure. Can you post some sharper images? Would be very curious about what's been going on inside your headlight assembly.
> 
> Looking back at some of the pictures I took of the insides of my own Xenon headlights, I have the exact same brownish color as do many others who have posted internal Xenon headlamp pictures. I contacted Daniel Stern to comment on why that's there -
> 
> ...


Having some issues downloading it from Apple's Icloud. Charles have a video of it. There are also lots of picture on BMW forum "headlight wiring flaking"

Only the wire going to the motor still has insulation becsuse I covrer them with heatshrink. I'm not sure but I think the flap solenoid insulation varnish caused of insulation failure. 









Look how light the brownish color the 1st time opened the headlight.










2nd time the headlight was opened










The reflector mirror finished was OK expept for the light rainbow color at the surface which is now color brownish. Yes, the brownish color is the basecoat.


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## Jezzie (May 24, 2020)

I just sent Daniel Stern a question about the stop/tail bulbs, because our Mk2 doesn't use the good-old 21W / 5W twin filament bulbs, but just a single 21W bulb that is dimmed using PWM for tail-lamp (5W) mode.

*Jezzie *- Replacing filament bulbs by LEDs - I missed any reference to the topic of pulse width modulation. While potentially adequate led replacements for the good-old 21W stoplight bulbs are available, on the Mk2 TT at least, the 21/5W stop/tail bulb is implemented by PWM control of a standard 21W bulb. Have you written anything on this topic?

*Daniel Stern* - 
This is (yet) another impediment to "LED bulbs" working safely, adequately, and legally in lamps designed to use filament bulbs.

> While potentially adequate led replacements for the good-old 21W stoplight bulbs are available
That word "potentially" is carrying more than its rated weight here.

> stop/tail bulb is implemented by PWM control of a standard 21W bulb.
True. That is a fairly common strategy, particularly on German cars. Most "LED bulbs" do not respond in the same manner as filament bulbs do.
Likely results are flicker and improper intensity in the dim (tail) mode.

Many thanks for your quick reply! So, no solutions to using LEDs in PWM circuits :-(

Correct. Keep in mind, the intensity ratio between bright and dim modes is _crucial_ to safe/effective/legal performance. "Brighter/dimmer" is nowhere near sufficient.

I really don't think this is worth being terribly sad about; spec bulbs work fine. Common sense says of course LEDs' faster rise time gives following drivers more time to react and therefore will surely reduce crashes, but that idea is frustratingly not supported by real-world data. See, for example, http://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/811712 , a major study of the subject.

The abstract of that study, from 2013, reads, _inter alia:_

===
_Overall, the analysis does not support a firm conclusion about whether LED stop lamps and LED CHMSL are more effective than incandescent lamps. The main analysis shows a significant overall 3.6% reduction in rear-impact crashes with LED. On the other hand, a non-parametric analysis not only fails to show improvement in significantly more than half the models, but actually shows an increase in rear impacts with LED for 9 of the 17 make-models that switched to LED. It was just the favorable results for high-sales vehicles such as Honda Accord that pulled the overall result into the plus. Furthermore, and perhaps most important, none of these 17 make-models is a “clean” switch pair that shifted to LED without changing anything else. All of the switch pairs shifted to LED at the same time that they changed the rear-lighting configuration and/or redesigned the vehicle. Basically, the crash data probably won’t support a firm conclusion until we have more switch pairs, including some “clean” switch pairs._
===

More recent thorough research (e.g., UMTRI) has likewise found no significant following-driver behavioural change in any way that would tend to reduce the likelihood of collisions with LED stop lamps versus incandescent ones.

> If it's ok with you I'll post this little conversation into the TT forum thread.

Go ahead…and then duck and cover!


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## SwissJetPilot (Apr 27, 2014)

*No longer able to ship Vosla H7's to the UK*

From *D92*

Hey so i emailed DS asking about costs for the Vosla H7's to the UK. This is no longer possible. Here are the replies and some information asking about best alternative bulbs to get after i asked about the Philips GT200's


_Oof…the UK part poses a hurdle. Since Brexit, the new rule is that anyone sending a parcel of goods—of any value—into the UK must register with the British Government and collect and remit taxes thereto. I am not willing to serve as an unpaid tax collector for a foreign government (or a paid one, for the matter of that), so I'm afraid I can't send bulbs to a UK address. :-(_

_Cheers DS_

*Best alternative bulbs to the Philips GT200's*

_The difficulty with the likes of the GT200 is the amount and depth of the blue coating on the glass capsule (and the extremely short lifespan). Better cost-effectiveness from Osram Night Breaker Silver (without blue gunk on the glass). Any of the bulbs claiming to produce "extra white" light (or super white, hyper white, platinum white, metal white, xenon white, etc) as its main promotional "benefit" is best avoided. _
_
It doesn't matter whose name is on the bulb -- Sylvania\SilverStar/Ultra or ZxE, Philips BlueVision or CrystalVision, Wagner TruView, anything from PIAA or Hoen,, Nokya, Polarg, etc. -- all the same scam. They have a blue-tinted glass, which changes the light color a little, but blocks light that would reach the road if the glass weren't tinted, so they give you less light than ordinary bulbs (not more). 

To get legal-minimum levels of light through the blue glass, the filament has to be driven very hard so these bulbs have a very short lifespan, and there's nothing about the tinted light that improves your ability to see -- the opposite is true (less light = less seeing, no matter about the tint). Sylvania got spanked to the tune of thirty million (!) dollars for false and misleading "upgrade" claims for Silver Star bulbs 

(see Sylvania taken to task for their false claims of headlamp superiority) -- and those are among the least-bad of an overall bad product category, so the maths kind of do themselves.

There is another thing you can do to markedly improve your seeing on dipped beam, without making any new problems: aim them appropriately.

New lamps or old, their aim is by far the main thing that determines how well you can (or can't) see at night. Regardless of the amount and distribution of light within the beam, the cutoff of a low beam headlamp, mounted 60 cm above the road surface (I haven't measured on a TT, probably lower than 60cm) , will intersect the road surface at:

86 metres in front of the car if aimed 0.7% down (0.4°)
60 metres in front of the car if aimed 1% down (0.573°)
46 metres in front of the car if aimed 1.3% down (0.75°)
40 metres in front of the car if aimed 1.5% down (0.9°)
30 metres in front of the car if aimed 2% down (1.1°)

The European regulations that govern how cars are built, resulting in that 1,0% spec on the TT's lamps, can diplomatically be called glare-averse, and can realistically be called glarephobic to a scientifically unsupportable degree. Rather than go off in the weeds with what could easily be a multiple-hour TED talk about it, I'll skip directly to a practical suggestion: most countries' vehicle inspection standards—including those of the UK—allow the low beams to be aimed as high as 0.5% down. But good luck getting a garage to set the lamps to match the callout (such as the 1,0% on the TT), let alone any higher; they tend to set the lamps a little extra low "to be safe", which is exactly opposite the real effect. Sometimes the callout on the car is moulded into the lens or housing, but often it's on a decal. 

If you were to some how or another obscure the moulded-in markings on the left and right headlamps, make decals of the attached artwork, apply them conspicuously near the headlamp aim adjusting screws (left and right), then present a TT for a headlamp adjustment and insist it be done strictly per the callout spec…well…see above: 43.3% increase in low-beam seeing distance. Glare will be well within appropriate levels, the car will be equally legal on the road, and high beam reach won't be materially different (no cutoff; much less effect of aim on seeing distance). Talk about a cheap and easy upgrade!
_
_Cheers DS









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