Regarding Center Top Vehicle Brake Lights - A Question - Page 1
Forum section: electronics / general

author: xrunner
author_rank: Super Contributor
timestamp: February 04, 2017, 01:08:42 pm
content: Short intro, my neighbor across the street was given a 2002 Hyundai Santa Fe by the family of the man that lived next to me who passed away this year. They gave it to him for helping all these years. The 2002 Santa Fe has only 17000 miles on it (wow), but it's always sat outside and looks terrible (paint looks like hell, etc). Anyways I've been trying to restore what I can otherwise such as the interior and wheels (looks good as far at that goes) in my garage this week for my neighbor - he's going to get it re-painted.Anyway ... I had noticed that the rear center brake light was not working and started to troubleshoot it. I eventually found out that the brake light switch by the brake pedal was the cause and simply re-seated the switch block. But I had noticed that this center rear brake light was an array of red LEDs (well they are clear lenses but emit red light). Even back in 2002 they were using LEDs - butONLYfor the center brake light. The left and right rear lights are bulbs. Well, ALL other lights on the vehicle are bulbsI also got a new vehicle couple of weeks ago - a 2017 Subaru Crosstrek. It uses bulbs for the rear left and right light sets but ... the top center brake light is LEDs.My question is, why LEDs for only the top center brake light? I have asked this question to several friends and my neighbor and no one can think of why the manufacturers want to use LEDs for the center top brake light.It's not mounted on the rear hatch, both are mounted on the frame either on the inside of the car (Santa Fe) or on the frame outside the vehicle (Crosstrek). My first idea was that if they had the center top brake light mounted on the hatch door it might make sense to use LEDs because they would be able to take the shock of the hatch closing ... but that isn't the case.Brightness? Nope - they aren't any brighter than the bulbs - about the same. I just don't get it. A 2002 and 2017 vehicle both use LED center brake light.Thoughts?

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: February 04, 2017, 01:33:47 pm
content: Its a safety issue. The center led light is sort of an optional thingy. It probably doesn't count during your anual safety inspection. A cop can't use that as an excuse for a routine traffic stop to see if he can take away your rights.

author: xrunner
author_rank: Super Contributor
timestamp: February 04, 2017, 01:36:40 pm
content: Quote from: joseph nicholas on February 04, 2017, 01:33:47 pmI'm sorry but I don't really understand your point. Can you re-phrase it?

author: nali
author_rank: Frequent Contributor
timestamp: February 04, 2017, 01:49:53 pm
content: It may have been to do with the legislation at the time - e.g. brake lights should be 21W etc etc.

author: Brumby
author_rank: Unknown
timestamp: February 04, 2017, 01:58:51 pm
content: In Australia (NSW at least) if any brake light doesn't work, it will fail the annual registration inspection.The location is related to the line of sight of following drivers - but the choice of LEDs is something I'm not sure about.There is one observation Icanmake, though....If you have ever noticed, incandescent light globes take time to reach maximum brightness. True, it's not long - but it is finite. LEDs are, by comparison, instant on. I find the difference not only noticeable on the rear of a vehicle, but a little striking. This would certainly be useful in achieving the objective - increasing the visibility and immediacy of the braking action of a vehicle in front.Here's a guy comparing the brightness of incandescent and LED lights - but it shows, very clearly, how much more quickly they turn on...https://youtu.be/9tbb5SjV48E?t=82

author: xrunner
author_rank: Super Contributor
timestamp: February 04, 2017, 02:05:13 pm
content: Quote from: Brumby on February 04, 2017, 01:58:51 pmIt's been passing state inspection here for years, the family just renewed it last year. Maybe the inspector didn't notice, or maybe the light was working at that time I don't know. My bet is, knowing the condition of the car, it wasn't working, probably hasn't for a very long time (due to the bad switch connection at the brake - not bad LEDs)QuoteWell if safety is top priority, one wonders why they don't use high power LEDs for the other brake lights. Instant-on and they don't burn out.I dunno.

author: NottheDan
author_rank: Frequent Contributor
timestamp: February 04, 2017, 02:27:47 pm
content: Could be a matter of certification. Using already street-legal incandescent lamps vs. the additional costs of getting new led lights approved.

author: nctnico
author_rank: Super Contributor
timestamp: February 04, 2017, 02:33:35 pm
content: Older LEDs put out way less light than a bulb so back in the early 2000's LEDs where not an alternative to bulbs. BUT LEDs have a narrower bundle so they appear bright to someone driving close by. I guess some car makers used LEDs to create a narrow bar which doesn't obstruct the rear view too much even though the light output is less than a bulb.

author: Brumby
author_rank: Unknown
timestamp: February 04, 2017, 02:36:26 pm
content: Quote from: xrunner on February 04, 2017, 02:05:13 pmTwo possible reasons -1. Legislation/regulations. Has any approval/standard been defined? Laws are slow to change.2. Light output. You can get plug compatible replacements from China - but their actual light output is well short of matching incandescents. They might be seem ok in the dark, but it daylight it is a different story. There would need to be some very strict guidelines so that only approved units are fitted.Just some thoughts.

author: xrunner
author_rank: Super Contributor
timestamp: February 04, 2017, 02:49:40 pm
content: FYI - Here is the 2002 rear LED array. As you can see, it's not thin and not really small. It could easily have had 4 or 5 bulbs the same size as the brake light bulbs in that cavity.The best explanation I've heard is -Quote from: Brumby on February 04, 2017, 02:36:26 pmAs far as light output - they are not any brighter than the bulbs, even on the new 2017. They are, or have been, set to appear just about as bright as the left and right rear "red" bulbs.Hard to imagine though, with all the changes in technology in vehicles (the 2017 Crosstrek has rear radar detectors for blind spots, front facing stereo cams for collision avoidance, navigation, etc ...) that somehow only the center rear brake light is still LED and not the left and right. Very odd.

author: Benta
author_rank: Super Contributor
timestamp: February 04, 2017, 04:55:58 pm
content: It's not that long ago that sealed beam headlamps were mandatory in the US. Regulations change slowly, and as the central brake light was a "new" thing, it got its own newer rules.

author: rrinker
author_rank: Super Contributor
timestamp: February 04, 2017, 05:03:28 pm
content: CHMSL out is definitely an inspection fail in this state. (Center High Mount Stop Light)LEDs possibly because it is harder to change bulbs out in there - your regular brake lights are easily accessible from the trunk on most cars, at worst maybe hidden behind a flap of carpeting. But how would you get in something tight up against the roof and rear glass? Also it's a very confined space, usually made of plastic, and incandescent bulbs of sufficient power to give the regulation brightness can get hot.

author: SeanB
author_rank: Super Contributor
timestamp: February 04, 2017, 05:06:10 pm
content: It is more a marketing thing, along with an added cost cutting. The marketing of "LED third brake light" was much more interesting to the consumer than "third brake light", as there were many vehicles with these, and many used incandescent lamps ( thanking you GM for this junk) for this.A benefit of using LED lamps ( and when the manufacturer specced the lamps they also spec a brightness bin as well, so all the vehicles in a series will have a similar light output during manufacture, as this is part of the QC on parts, just that as led tech improved they moved down from best in batch, to mid batch, then finally lowest in batch) is that the current draw is lower. This means both a cooler running housing, so you can use a regular blend as used for the rest of the interior, instead of needing a high temperature plastic compound to prevent warpage. With this you also have lower current draw, under 2A for any light bar ( and some are really long and bright as well) as opposed to using up to 100W of incandescent light in a housing, which needs both heavier wiring in the car, a brake switch rated for this massive extra current draw, higher current fuses and supply wires and in many cases a BCU firmware change to handle reporting lamp failure. LED lamps thin wires, no heat sourse and no extra load over switch rating, plus BCU will still provide bulb out warning if the model has it.

author: IanB
author_rank: Super Contributor
timestamp: February 04, 2017, 06:58:23 pm
content: I have observed a trend towards all LED lighting on new vehicles, especially on brands like Honda. Therefore if a new vehicle is still using bulbs for the tail lights or brake lights I can only assume it is for design or cost reasons. To switch over to LEDs the manufacturer has to redesign the lamp housing, change over the factory tooling and line up a new supply chain for the lamp units. It is probably not convenient to do this until they go through a major model refresh.

author: NottheDan
author_rank: Frequent Contributor
timestamp: February 04, 2017, 06:59:40 pm
content: Quote from: rrinker on February 04, 2017, 05:03:28 pmNot a very convincing argument, considering that in some cars you almost have to disassemble half the front to change out headlights.

author: SeanB
author_rank: Super Contributor
timestamp: February 04, 2017, 07:30:41 pm
content: Quote from: NottheDan on February 04, 2017, 06:59:40 pmWell, they were designed so the lamps would last the manufacturers desired lifetime of 3 years, and then you would either buy or lease a new vehicle.French and Italian design at it's finest. Just wait till you have to replace those "lifetime" HID and LED assemblies, which often are a single part consisting of the lamp, driver and headlight housing, with levelling motors and controller, all as a single part replacement. And there to replace you often find you need to remove the inner fender liners, lower covers, engine inside covers, battery and then the bumper skin complete to get to the retaining bolts, plus have to integrate the new unit into the car bus afterwards.Peugot/Renault/Citroen has headlamp replacement on some models booked as a 3.5 hour job, and at that rate you change both bulbs and all others in the clusters at the same time, just to have new lifetime units. not fun doing it again a week later. At least the VW van at work changing them is a tool less affair, just pop the old ones out and put a new one in, to get the orange "lighting system fault" light off the panel. Jees guys, you have a graphical panel there, and a computer, which is programmed to display umpteen languages, and it drives the indicator lamps as well, why not use the thing to give slightly less cryptic messages than the manual has. not like there is a limit of 512 bytes in eeprom space you can put on the bus is there. St micro is almost de facto in these, and they will handle 4M no problem, you can put the entire manual in that space, and leave room to fly to the moon as well.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: February 04, 2017, 07:34:57 pm
content: It's all about the speed of illumination. The faster turn on time of LEDs translates to a extra feet of stopping distance at freeway speeds. Could be the difference between a crash and just a hard stop.No idea if this was legislated or what. A Hyundai is a rather inexpensive car to have such a new feature.

author: james_s
author_rank: Super Contributor
timestamp: February 04, 2017, 07:36:17 pm
content: The inspections are pretty lax here, my state has no safety inspection at all, just an emissions test every 2 years for cars older than a few years and less than 25 years old. A burned out brake light can get you pulled over but in most states there's nothing to stop you from licensing it.As far as why only the center brake light is LED, it's likely a matter of cost. Conventional bulbs are cheaper for the main integrated brake light but the center one can be LED, getting the advantage of faster response for the cost of only a single light assembly. If you consider that the main taillights generally have marker, brake, turn signal and reverse lights all in one unit, it would cost substantially more to make those all LED, especially back in 2002.

author: GreyWoolfe
author_rank: Unknown
timestamp: February 04, 2017, 08:39:41 pm
content: Quote from: FlyingHacker on February 04, 2017, 07:34:57 pmSWMBO has a 2006 Monte Carlo that has regular bulbs and LEDs for the 3rd brake light. It is mounted in the trunk lid and there is a cut out in the bottom of the spoiler/wing. At least externally, it takes up little space. It's long and thin and also lights up a fraction before the regular brake lights.

author: Someone
author_rank: Super Contributor
timestamp: February 04, 2017, 09:08:42 pm
content: I dont recall anything in the internationally harmonised ECE regulation 84 that requires or prohibits specific light sources, as long as they meet the technical requirements. There are cars with LEDs for all the rear facing signals, and failure is by replacement of the entire module (expensive). So it may just be that the lifecycle/warranty costs are cheaper with the incandescent bulb in reflector style for the wide angle lights.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: February 04, 2017, 09:59:37 pm
content: This is my 2 cents on the reason.1. The housing and parts for these need to be light weight, since they are either mounted on the back windows or on a fin etc.2. The parts are cheap.3. LEDs light up faster than incandescent bulbs.4. Incandescent bulb holders are metal by nature and and make the geometry more difficult.5. The assembly is probably purchased from a outside vendor and this is the most efficient and effective means in which to get the assemblies.I see all vehicle turning to LEDs in the future.

author: VK5RC
author_rank: Unknown
timestamp: February 04, 2017, 11:14:12 pm
content: I thought the reason LED 'bulbs' were slow to take market hold was due to the relatively poor radiation pattern i. e. put most of the light out in a 30 degree arc or so. For an eye level brake light that is not a problem but for a turn indicator and the rear side brake lights I think it is. The incandescent bulb radiates widely.I find the newer LED indicators are not easily seen esp from the side and in bright sunlight.

author: james_s
author_rank: Super Contributor
timestamp: February 04, 2017, 11:42:22 pm
content: If they're properly engineered then the radiation pattern can be just fine, but they still cost more than an incandescent indicator. It's the LED retrofit "bulbs" that are particularly crap and not legal for street use.

author: Halcyon
author_rank: Unknown
timestamp: February 05, 2017, 01:56:14 am
content: I think there are a lot of misconceptions and "guessing" going on here.Using LEDs in tail lights is something that has been changing recently. You'll find a lot of modern cars and not necessarily just the mid-to-high end market have begun using LEDs in lieu of incandescent bulbs. Of course the whole light fixture required a complete re-design in order to satisfyAustralian Design Rules (ADRs).The two main reasons why it hasn't become mainstream up until now is that the incandescent bulb offers a greater degree of visibility around the vehicle so those driving beside the vehicle still see some light output (specified in the ADR) and they are much more resilient to under/over voltage conditions due to faults or poor designs. They are also cheap as chips and don't require manufacturers to modify their designs too much.With respect to traffic laws, they differ widely between countries (and in some countries, between states). If you're going to post legislation, it would be helpful if you can provide sources. People tend to take hearsay as being true a lot of the time (for example, in Australia, it'snotunlawful for passengers to consume open alcohol in the car. Aussies commonly refer to them as "roadies" or "roadys").Australia has a fairly standard set of Road Rules and traffic legislation (with some state-specific rules or exemptions). There are many reasons why Police can lawfully stop you. The two main ones are under the Road Transport Act 2013 (AU) which allows for Police to stop any vehicle for the purpose of submitting the driver to a random alcohol (and/or) drug test or inspect a vehicle for the purpose ofdeciding its identity, condition or the status (whether in this jurisdiction or another jurisdiction) of any registration or permit relating to the vehicle(this includes also being able to enter the vehicle).Generally speaking, when it comes to vehicles and road safety in most Western countries, you can bet there is a rule or instrument in law which addresses it.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 05, 2017, 02:30:52 am
content: I can't speak to the actual why of this usage in any country, but I can tell you what the trade magazines here in the US said as LEDs started to be used in this third light application. The regulation requiring a third brake light happened in the mid-1980s in the US. Early implementations were late additions to the design and were an incandescent bulb in a box on a stalk sitting in the rear window for most cars. As new cars were designed the lights were better integrated into the cars design but were still an incandescent bulb in a box. This was before the light output of LEDs was ready for this kind of application.The trade journals sometime along here started reporting that LEDs would start being used for third brake light applications because the narrower form factor that could be achieved with them allowed better integration with styling. The long life of LEDs helped here also because room for mechanisms to replace bulbs didn't have to be arranged. A long narrow strip also allowed for a lot of relatively low output LEDs, consistent with the technology of the time. I think I also recall a bit of back and forth with the regulatory agencies about whether the narrow and wide format would meet the functional requirements, and words about the third brake light application not requiring broad beam angles since it is almost entirely intended to reduce rear end collisions from a following drive.That is consistent with the story of how LED lights have shown up in vehicle applications here in the US. Initially in narrow third brake light bars. Then as LED cost came down in more shapes of brake light bars. Still later with more brightness and even lower costs starting to show up in brake lights and tail lamps. And now starting to appear in headlights.So the story would be more of styling, technology and price than in safety differences or regulatory demands.

author: xrunner
author_rank: Super Contributor
timestamp: February 05, 2017, 02:33:04 am
content: Very informative - thanks!

author: VK5RC
author_rank: Unknown
timestamp: February 05, 2017, 10:59:18 am
content: @xrunner if you can't get to sleep; re vehicle standards I was interested to see a quite reasonable attempt to Internationally harmonise 'standards', since 1958 !https://www.unece.org/wp29.html.- amazingly sensible. Most of the amendments seem to be in the 1995+ time frame.

author: Seekonk
author_rank: Super Contributor
timestamp: February 05, 2017, 11:48:01 am
content: The real reason is they don't have the space there to mount bulbs. One year or two years of the Ford Explorer they used a fluorescent lamp. These were nearly impossible to get as there was not enough demand to make aftermarket ones. The lamp cost about $300 and the power supply was mounted down in the hatch cover. Figuring out which one was bad was expensive. Many cut open the light and just put LED in so they could pass inspection.

author: Halcyon
author_rank: Unknown
timestamp: February 05, 2017, 12:00:00 pm
content: Quote from: Seekonk on February 05, 2017, 11:48:01 amNot to mention Fords are known for electrical issues. In my state, we have yearly inspections for light vehicles over 5 years old, but you still see Ford after Ford with completely non-functioning brake lights, the indicators/reverse lights come on instead of brake lights or they do some kind of strange random dimming of other lights.Subaru is another car I've noticed that seem to have a high proportion of blown lights. It's usually one of the side brake lights or headlights. I would probably say in any given week 10-20% of Subaru Foresters or Libertys I see on the road have something wrong with their lights.

author: xrunner
author_rank: Super Contributor
timestamp: February 05, 2017, 01:08:14 pm
content: Quote from: Seekonk on February 05, 2017, 11:48:01 amThey sure do have the room, you must have missed my post where I showed the 2002 Hyundai rear center brake light assembly. I've attached it again here. It plenty large enough to mount bulbs in. It's not only large enough top to bottom and lengthwise, it's also a pretty deep enclosure. Even if it needed to be even larger for some reason, that would not have been a problem to design at all.Edit: As a matter of fact, the size of the thing (I've taken it apart in the troubleshooting process for the original problem) is seemingly way bigger than it needs to be inside.

author: Brumby
author_rank: Unknown
timestamp: February 05, 2017, 01:11:20 pm
content: Quote from: Halcyon on February 05, 2017, 12:00:00 pmOdds on the cause will be a bad earth.The globes will be fed separate power, but they will have their earth sides connected together in the fitting with a common lead to an earth point on the body. This earth connection will go bad and the powered globe will find earth through the other globes. Depending on the circuit topology and exactly where the earthing fault occurs, you get some weird results.

author: james_s
author_rank: Super Contributor
timestamp: February 05, 2017, 09:04:58 pm
content: I've seen that in a lot of different cars due to bad grounds. I actually don't recall ever seeing it in a Ford but I haven't really paid a lot of attention. I suspect it's a lot more common in areas where they use salt on the roads. Perhaps Ford grounds the tail lights in an area that is vulnerable to salt corrotion.