Bosch H4 Lighting

by Richard Atwell
(c) Copyright 2006-2011


Update 01/15/10:

Bus Depot currently has Bosch H4 headlights on sale at $44.95 FOR A PAIR! This is 1/2 price. You can also buy them from Cheri at

Get them while you can....

Why should you upgrade your headlights? For the simple reason that the lighting that VW equipped every US-based bus and bug with is based on 1940s sealed beam technology. These tungsten sealed beam headlights do not do a good job of illuminating the road at night and you can easily outdrive them at 70mph which is to say you may not see road hazards until it's too late. You'll also find that your night vision gets worse as you get older which compounds the problem. A popular upgrade is to switch to H4 based lighting used throughout Europe.

Design Differences:

Sealed beam headlights are just as they sound: like an incandescent light bulb in your house, an exposed filament is sealed inside the housing with a vacuum. The style is evident in the typical Sylvania 6014 bulb you will find on your bus if you remove the headlamp to inspect the backside.

While very rarely used on modern vehicles, The 7" round headlamp was standard equipment on millions of vehicles worldwide, including tens of millions of VWs until USA requirements were relaxed in 1983 when replacement bulb headlights were legalized which allowed the lamp designs to improve. While there have been many improvements in lighting technology over the years, two are relevant to VWs which use the 7" (178mm) round style lamp:

One innovation came in the form of a sealed beam partially filled with a halogen gas (banned in USA until 1978). Light output increased but the basic design of the headlight (Sylvania H6024) limited the improvements that could be made.

In 1971, the H4 style headlamp was introduced in Europe. These headlamps were meant to be high quality productions designed to last the life of the automobile by using a replaceable quartz halogen bulb.

While both styles rely on 55/60W bulbs, the design of the H4's reflector, lens and the position of the bulb produce a superior beam to the DOT sealed beam headlamps used in USA. I'll refer to these H4 units as European E-code headlamps because they are the most popular.

So how does the light output differ?

sealed beam design H4 low beam H$ high beam
Sealed low and high beams H4 low beam H4 high beam

You can see from the diagrams that the sealed beam reflector has the potential to produce more light output because the entire reflector is used. When switched to high beam however, the light pattern cast is simply shifted due to the position of that filament from the focus point of the reflector and as such the design of the low beam and high beam must be a compromise to avoid on-coming glare.

It's often argued that ECE is no better than DOT but the designs are clearly unique and there is an critical difference. The sealed beam design has no ability to provide a sharp cutoff between the light that the driver wishes to see cast and the light that the oncoming driver does not wish to see. In other words, there is less glare from ECE lighting than DOT.

With the H4 this is achieved in part by the design of the reflector (light gatherer) and lens (light director) but also in part due to the shield that lies below the H4 filament. Because of the shield used on the H4 bulb, the H4 reflector/lens can be optimized for both low and high beams which is an overall design advantage. The most popular beam pattern of this style is known as the ECE lighting pattern and it is better for everyone on the road: drivers and traffic.

H4 vs. Sealed Beam:

Wondering how the sealed beams fare against the H4s?

sealed on low H4 on low

As you can see the difference is dramatic with the H4s. Vision is improved through brighter lighting and better coverage. (Note: the sealed beams were installed after the headlight buckets were aimed for the ECE lamps so the actual position of the sealed beams will vary slightly from the photo when properly aimed).

Unfortunately for aircooled VW owners, the US Federal Motor Vehicle Safety Standard (FMVSS108 code) was not updated by the time our buses ended production in 1979 which mandated that sealed beams be used despite their inferior design. This means that VW could only install E-code lamps into baywindows destined for non-US countries. The end result is that US part catalogs only show which sealed beams lights to use on VWs when searching by make, model and year.

H4 lighting is available from Bosch, Hella, Cibie and other manufactures but the three I mention and the most reputable. Bosch and Cibie produce the best output and value for your money. Some HB2 based DOT lamps are available but for the E-code lamps you usually have to turn to the internet to locate them.

Auto vs. Motorcycle:

For several years I've been recommending people buy Bosch 0 301 600 118 units. I can't remember how I located the part number but I purchased my units from a local dealer after confirming the part number with a Bosch wholesaler. Word spread about the improvement in vision and I started to notice many Bosch vendors listing them in their catalogs.

These European E-Code Bosch H4s are labelled "DOT" and "motorcycle" in tiny lettering. While this labeling has never worried me because the lights work so well, once in a while someone will bring up the issue that, "the optics (and resulting beam pattern) are grossly inferior to the auto unit for lighting the way ahead while driving a car".

Well, autos and motorcycles are certainly different vehicles so on the surface it appears to be a valid concern but what is the real difference? Let's compare two units from the same manufacturer: Bosch.

The auto version is very hard to obtain in the USA because Bosch doesn't offer a US automotive lighting catalog like it does for other countries. Parts like this often have to be imported directly from Germany and only some importers can do it.

Luckily, right after "yet another online flare up" on this very issue, I found myself in Switzerland during vacation and within two hours of arriving at my destination, I had located a Bosch dealer with this Euro only part in stock.

Bosch boxes

Both lamps come in traditional Bosch packaging that say Made in Germany but each lamp is labelled Made in Sweden where the part number is stamped. The lamp on the left was bought for $39 in USA. The lamp on the right for $42 after converting from CHF.

DOT H4 reflector Euro H4 reflector

The bodies have an identical shape but upon closer examination there are subtle differences.

First, the sealing gasket for the Euro unit is larger and has two holes to allow for moisture to be vented and drained. Someone once told me that the Euro version will fog up anyway but I haven't had this experience trying both headlamps in various climates long term so in my opinion this is not enough of a reason to pick one unit over the other.

DOT lens Euro lens

While both lamps look similar from the front, there is a characteristic difference that distinguishes each unit: the Euro unit has a built in shield that covers the front of the bulb. One of the purposes of the shield is to limit unreflected light from the low beam filament. The reason it is not present on the motorcycle unit is that the shield is not designed for the vibration produced while riding which may cause it to break away.

Some H4 lamps allow the bulb to seat on the base of the reflector but both of these units have cast base that permits heat to dissipate through the back of the lamp rather than through the reflector causing it to distort.

Aside from the shielding, the lenses are similar noting that the DOT unit has some more refracting elements just below the center where the H4 logo is seen. Both units project the ECE lighting pattern.

Both units have various H4 and E markings but the motorcycle unit also says SAE M76 DOT Motorcycle which means that is conforms to the SAE M standard of 1976. The auto units do not have DOT markings on them (they are meant for Europe after all).

I'll also mention that there is another 7" round Bosch H4s that is available: it is identical to this auto unit except that it has the additional plug and bulb for the parking (aka "city") light. The auto lamps above can also be purchased in a two pack which include two Osram bulbs. See end of this article for part numbers.

Head to Head:

I'm still waiting to obtain some photometric data from Bosch so in the meantime I decided to test the lighting head to head to see how each unit actually performs. Using the same bulbs and with the engine running (14V at battery), I swapped in each type of lamp shown above to generate various lighting situations to demonstrate how the light output differs.

Tests were conducted in as much darkness as possible (10pm, no street lighting) with my digital camera mounted to the dash and configured for manual settings to reproduce the conditions for exposure. I used the driveways and parked vehicles as a visual guide to show the reach of each beam and the images are from the driver's POV.

Trivia: the house to the left of the photo (not shown) has the famous garage where the two Steves started Apple Computer. That oil stain in the photo is where Steve Jobs used to park his old splitty :-)

I marked the road with chalk to make sure I parked in the same spot (you can see the oil stain in the photos verifies this). Finally, I aimed the headlamps according to the ECE method before the test.

So how do they differ? On the left is the motorcycle unit and on the right the auto unit from Europe:

motorcyle H4 low auto H4 low
motorcycle H4 high auto H4 high

Low beam is virtually identical and not surprising given the similar design of each unit (ignoring the lower half of the lens which is only used on high beam). On the high beam there is some difference with the edge given to the motorcycle lamp (there appears to be more coverage yet notice the mail boxes on the left in both photos are reflecting back the same amount of light). Given that we drive on low beam 99% of the time, it's really splitting hairs in my opinion to claim the motorcycle lamp is unsuitable and on hi-beam I think the motorcycle lamp is equal or better to the auto lamp. QED.

There are numerous technical differences between the two units having to do with intended application and regulations but in practice during clear or inclement weather, driving with each lamp installed in the baywindow bus, there's is virtually no difference.

Having driven many motorcycles with H4 lighting before installing this style of lamp on my bus I've grown accustomed as what to expect from H4 lighting. My belief in the suitability of the motorcycle labelled H4s on the VW bus has never been in doubt but now we have some evidence that the Bosch H4 motorcycle lamp, while different is not grossly inferior to the Bosch H4 auto lamp.


Because of the stubborn federal regulations, the H4 E-code lamps that are imported are often the motorcycle variety and labelled as such and/or sold with the warning that they should be used off-road only. E-code lamps are legal to use in Canada these days so hooray for Transport Canada who has seen the light, so to speak. Specifically CMVSS 108.1 permits the usage of E-code headlamps that lack DOT markings.

Until 1983 auto makers were not allowed to install replaceable bulb headlamps (RBH) into US vehicles according to federal law (FMVSS108). When they did they created their own bulb standards (HB2/9003) which while similar was different enough and naturally required a bulb specific design and reflector to produce the DOT beam pattern. In 1997, the laws were further relaxed to permit ECE style lighting patterns.

With all these standards and regulations (SAE M, ECE, H4, DOT, etc) the comparison of products simply based on the labeling gives rise to uncertainty. This is complicated by the fact that the regulations are hard to read and make it less than clear how the rules should apply to older vehicles. Couple this with the fact that testing standards are obscure and that manufacturers tend not to fully label their products and you have a confused consumer.

Since these laws govern vehicle manufacturers and not drivers, it can be difficult to determine whether or not you can use H4s on your bus where you live. When laws change, it's also up to manufacturers to retest and re-certify and relabel their products which means while they may be technically confirming, they remain otherwise because they see no need to invest in the USA market to provide two styles of headlamps.

Because the 7" round headlight is virtually out of fashion only finding use on a small number of new model motorcycles, the law has not surprisingly remained just as out dated as the lighting has become. While the government has strived to protect you from yourself, in this case, it's clear to everyone mounting quality constructed European standard H4 lighting that they are doing the world a favor by adopting this lighting system. The laws exists to prevent substandard lighting from being used but it's also successful in limiting improved lighting from being adopted.

Luckily there is relief for some who are truly concerned about staying within the law: it is state law that matters to drivers and some states explicitly permit the use of E-code lamps to improve safety in poor weather conditions. Unfortunately other states continue to follow the federal guidelines and forbid it. Some states have updated laws but require you to install the same equipment that the factory used (sealed beam in our case). While there is a lot of below spec aftermarket lighting out there for sale, be assured that these Bosch H4s are far superior to the legal sealed beams the government expects you to use.

Since 9 of 10 states no longer require headlight inspections you don't really need to worry about getting stopped with the wrong lights (just swap in a set of your old sealed beam for any tests you have to take if that's the case). On the road, while abnormally bright lighting used to draw the attention of law enforcement to your vehicle, the superior ECE lighting pattern keeps the light on the road and out of the eyes of others. Another benefit is that the majority of cars on the road have equally bright or brighter Xenon/HID lighting now so you'll simply blend in and go unnoticed (unless you plan to caravan with a bunch of 6V beetles :-)

And of course, if you are driving a motorcycle, using an E-code H4 is legal in USA and Canada.

The Devil in the Details:

If you buy a Bosch E-code motorcycle H4 and put it in your bus, report on the favorable result to your favorite online forum, chances are that someone will bring up one or more of the issues below to make you doubt your purchase (I can only vouch for the two Bosch units as the tests above verify so keep that in mind when discussing the various issues below). Let's examine each issue in detail and see if there is any merit to any of them.

The motorcycle lamp is incorrect for an auto resulting in grossly inferior beam pattern because of the lens.

I've yet to meet anyone that can back up this claim with some hard data. With so many brands I wonder if it's even possible to be 100% certain about this. If it is the case for DOT lamps I can understand but for the E-code lamps I tested, the test result speaks for itself.

The motorcycle lamp is mounted in an different position than an auto headlight.

Although not obvious, the headlamp on the bus is mounted far higher than your typical auto. In fact the center of the bulb is roughly 33" above ground after the driver gets into the cab. That's the same height my motorcycle H4s are set at before I get on the bike and compress the suspension. To give you a reference, an old 80s BMW 325i has the headlamps set at 23" above ground.

The guidelines for lighting state that a road going vehicle needs to have lights at least 22" above ground. Common sense would also dictate that there are a variety of body styles and mounting locations and so headlamp aim would be more important than mounting height and so it is.

One side issue is the fact that a motorcycle is a single track vehicle while an auto is dual track. These are terms that only the government uses in their documentation. I've never really understood the difference because a motorcycle can ride anywhere in the lane and riders are taught to do so. Therefore it is easy for the motorcycle headlight to be in the same position as the driver's side headlight on the bus.

What about the fact that the lighting is brighter because there are two bulbs in use? Many motorcycles comes with two bulbs and while the separation between the two is much less than the bus, the distance L to R seems minor compared to the distance the beam has to reach down the lane. More importantly if the ECE lighting pattern is doing its job, glare won't be an issue unless the lamps are so improperly aimed as to bother oncoming traffic on low beam.

H4 lighting may or may not pass local state inspection.

This can be a concern depending on where you live. I've read that some states (NJ, PA, VA, MD) specifically prohibit the use of E-code lamps. Others (OR, WA) permit their use because they are better in weather conditions that generate low visibility conditions. Why are improved lights suitable for some states and not others which have to be mounted during all weather conditions? It's an idiotic old-tyme law that some state bureaucrat didn't take the time to update when the technology changed.

Another difference is that DOT lamps have little bumps on them which are used for aiming purposes. E-code lamps are not aimed this way and as such you would fail such an alignment inspection.

Practically speaking, to pass your inspection you only need to swap in your sealed beams to pass the test. By doing this you are deciding that the lights that are good enough for 600 million Europeans, Canadians (and Americans in some states) are good enough for you also. I've also read that only about 5 states bother to do headlight inspections anymore.

The motorcycle bulb won't pass inspection.

The H4 bulb is the same whether or not it is used in an auto or motorcycle lamp. The design of the bulb is standardized and has a specific base (P43t - 38) which determines how it will mount in the lamp. Some bulbs are marked DOT and some are not. Some DOT bulbs look like H4s but they are likely labelled HB2/9003 and are not exactly the same.

In reality the chance of your bulb being inspected is at lottery winning odds and isn't an auto vs. motorcycle issue anyway.

The motorcycle label on the lens means it's unsuitable for use in an auto.

The reason for the labeling is a requirement according to FMVSS108:

S7.9.5 Each replaceable bulb headlamp that is designed to meet the photometric requirements of paragraph S7.9.1(a) or paragraph S7.9.2(a) and that is equipped with a light source other than a replaceable light source meeting the requirements of paragraph S7.7, shall have the word "motorcycle" permanently marked on the lens in characters not less than 0.114 in. (3 mm) in height.

Section S7.7 talks about replacement light sources, makes no mention of H4 type bulb and says such lamps have to be marked with the words motorcycle if the bulbs do not meet the requirements. This marking alone doesn't specify that the lamp may only be used on a motorcycle nor is there any mention in the regulations that a lamp marked as such would be unsuitable on a auto. It only says that lamps meeting the motorcycle requirements must use a bulb that meets S7.7 or the label must apply. Further, because section S7.9.1 says that motorcycles may use 1/2 of an auto lighting system the distinction between the two systems is blurred even further. It's not clear to me exactly why an H4 bulb would or would not conform to section S7.7.

E-code lamps made for a British auto (RHD) won't work in USA vehicle (LHD).

This is true and indeed a concern when buying H4s. Certainly the two part numbers I've provided are for LHD vehicles but RHD units are out there for sale. Just because a pair of H4s come, for example a vendor of British car parts, doesn't mean they were intended for RHD (UK, Australia, Japan) markets. Many British cars were exported to USA and in 99.9% of cases they were installed with the correct lights. However this is something that you should confirm especially when buying parts over the internet.

What can be confusing while searching are the terms themselves: remember that driving on the right is done in a left-hand drive (LHD) vehicle.

The motorcycle lamp lacks the shield between the lens and the bulb (due to increased vibration) so this means the projected beam is different.

The shield is indeed only installed in the automotive version but since some motorcycle lamps lack the shield with their H4 lamps while other don't, this by itself doesn't indicate that the light output pattern is only suitable for a motorcycle. The lens may very well need to be changed to accomodate the reduction in light but when you consider that only a small percentage of the light emitted by the bulb comes from the center of lens (observe the coating on the bulb itself) this isn't a major factor.

If the shield manages to reflect some of the light it's blocking back to the reflector then there maybe no loss but you still have to consider that the front of the bulb is coated and only a small percentage of light will reach the shield. In testing, you can see from the low beam photos that this is a non-issue.

I've read one report that removing the shield (if even possible) improved the beam by filling in the center slightly but I haven't verified it. At least from the photos above, I can't tell what difference the shield is having on low beam.

There are clauses in FMVSS108 that forbid the use of H4s on autos.

The regulations state which parts, so labelled are allowed to be used. It primarily refers to the US standard (HB2/9003) replaceable bulbs only. It cannot be interpreted to mean a part is acceptable because it wasn't specifically mentioned as banned but there is some wording (such as "other types of replaceable bulbs") that might allow any H4 to apply. The argument against this is the fact that the HB2 was designed to be a US version of the H4 as far as I understand. There is also a distinction to be made between a DOT H4 lamp and an E-code H4 and FMVSS108 seems only to permit the use of DOT lighting. In other words, if it lacks the DOT label, they are restricting use.

It's also important to note that FMVSS108 applies specifically to auto manufacturers so check your state law to find out what you are actually permitted to use.

Vendors state H4s are for off-road use only so they can't be legal for road use.

Vendors like to cover their butts and you would too. People are going to do what they like with the parts they buy and adding this tiny disclaimer is far easier than actually researching the laws for every state and comparing them to your shipping address.

The motorcycle lamps are not compliant with FMVSS108 for use on autos even if they are marked "DOT".

Historically, lighting has required DOT labeling for both kinds of vehicles. The labeling requirements per application are subject to the photometric requirements and motorcycle headlamps are required to meet the SAE J584 standard. Auto lamps must adhere to another standard to obtain DOT labeling but the proof (via standards) that a headlight can't be built to meet both standards hasn't surfaced because the standards refer to DOT lamps while we are trying to compare the E-code designs.

Bosch automotive H4s with DOT markings are again, legal under FMVSS108.

Bosch does not make a 7" round H4 with DOT markings although they do make the E-code H4 for autos shown in the above photos. Please forward me a part number and photo if you have proof otherwise.

An ECE lamp which is SAE M compliant but not labelled motorcycle is not a dedicated motorcycle headlamp which can be used on an auto.

This is a thorny one. While both headlamps were built to the SAE M standard, the argument is being made that the motorcycle labeling supersedes the applicability. This isn't the case as SAE M simply refers to the SAE J584 test standard.

This comes up as an issue with people who are using other brands of ECE SAE M headlamps and believe they are intended for automobiles when in fact they are another headlamp originally intended for motorcycle. The fact that they are missing the DOT and motorcycle label only means they were destined for sale in the European market but they are still SAE M lamps. One such example is the Cibie HCR 7" round headlamp.

An E-code SAE M motorcycle lamp can be marked DOT because ECE lighting is allowed under the regulations. Conversely, an E-code SAE M lamp which isn't marked DOT isn't a defacto auto lamp.

An ECE SAE M lamp with no DOT markings can comply with both motorcycle and auto standards yet an ECE SAE M lamp labelled "motorcycle" cannot.

Again, the SAE M standard determines the beam pattern, not the labeling.

The motorcycle beam pattern is not optimized for use on an auto, even though it is ECE and SAE M compliant.

This was partially covered above. If a headlamp is SAE M, it conforms to SAE J584 which is the motorcycle standard. The beam pattern of any SAE M lamp cannot be distinguished using the "motorcycle" labeling alone. On low beam, there is no measurable difference.

A lamp designated "motorcycle" when used on a auto will cast more upward stray light, which increases glare according to FMVSS108 test requirements.

While this might be the case for a DOT lamp which the regulators are referring to via DOT testing procedures, the ECE lamps are a completely different design and their sharp cutoff limits glare in a way that no DOT lamp can achieve.

Is your head is spinning trying to read all that? I'll never understand why some people are so hell bent on using regulations and theory to tell you that the lighting you know to be excellent and safe, is otherwise.

Wiring requirements:

Since the reflector and lens are so efficient, only 55/60W bulbs are required when installed H4s. This is the same wattage as the stock bulb so no fuses or wiring will melt.

If you upgrade to higher wattage 80/100W bulb then it is recommended that you run dedicated wiring and relays to avoid electrical fires. Several webpages exist that depict how to do this best however I think it's an unnecessary expense unless you are planning to take your bus off road where there is no street lighting. Keep in mind that the extra heat output might damage the lens because it might not be rated for such a high wattage bulb.

Battery voltage:

Light output, or luminous intensity drops off faster than the voltage drops because of the relationship between the two. Here's what happens according to Hella:

Lighting is designed to operate near the 14V your alternator puts out.

If you are only getting 12V from the battery when the lights are on, you will only be producing 1/2 of the possible light output.

Relays used with stock wattage bulbs can bypass the high resistances in the headlight circuit and send as much voltage to the headlights as possible maximizing the light output. Before investing you should seek to determine why your voltage is low (possibly due to poor grounds in various parts of the electrical system or an alternator and/or voltage regulator problem exists).

Other brands:

Stay away from the cheap $25 units because the reflectors flake and they have poor light scattering characteristics (some units don't even fit the headlight bucket). Some have even reported that the light output from these low cost units is worse that the factory sealed beams!

Also be on the look out for lamps meant for UK and other countries where they drive on the left side of the road (RHD). Because the lighting pattern is always asymmetric, you will be casting more light on oncoming traffic and less on the road ahead.


Lighting is a vehicle safety issue, so my advice is not to cheap out because in practice, 1/2 price means 1/4 as good when it comes to lighting. $100 is all that it costs to get the best.

Lamps: buy Bosch 0 301 600 118 units ($40/ea). Bosch engineered these lamps for a lifetime so invest the extra $15 they cost.

Bulbs: get standard 55/60W Made in Germany bulbs from Sylvania (H4BP) or Osram (64193 or 94193) at your auto parts store for $9/ea because they have long life. Osram owns Sylvania, btw.

Osram box Osram label

Sylvania package Sylvania notes

Bosch, Narva and Flosser are other quality brand names but difficult to locate in USA. The rounded bulbs are usually non-halogen types (avoid).

I find the Sylvania bulbs at Kragen, Autozone and Pepboys but stocks are often low or have run out so call ahead. In my experience, Osram bulbs are harder to find unless your auto chain stocks a lot of alternate brands.

Why do quality bulbs filter UV light?

The UV filter is a feature that protects plastic lenses on motorcycles from degrading.

Your H4 lamps should have glass lenses and this is less of an issue.

Stick with standard halogen color temperature bulbs. Extra white and blue bulbs can make the road harder to see: whiter isn't always brighter but the brain is tricked into thinking so.

If you have to "super-size" your purchase, get Silverstar H4s (64193SVS) from Osram although they will cost about double the normal bulbs. Sylvania made Silverstars are not the same bulb (look for bluish glass) and they tend to burn out quickly according to many reviewers. Reviews are mixed because the same brand of bulb comes from related companies which are selling different products.

Bulb Life:

Stock wattage bulbs are bright, engineering for long life and offer the best view of the road according to the experts and the best value. The bulbs I'm using are the original ones I put into the Bosch H4 lamps. The headlights in my wife's car which have daytime running lights have been going for 12 years now.

Warning! NEVER touch the glass of the bulb with your fingers. It's made from quartz and when it gets hot it will react with the salts your hands leave behind and cause the bulb to fail prematurely.

Part Numbers:



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