Headlight bulbs

[Sierra1]

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Why a twin headlight like the S10 blow 2 bulbs close together - because both bulbs have endures the same conditions - both always on and vibrating.

other cars/bike with dual headlights (separate low and high beams) will not blow both bulbs together as you use the high beams bulb less so it lasts longer.

as a general rule, I replace both similar bulbs together for this reason, if one low beams blows I replace both. same with high. I keep the old good globe as an emergency spare.

::026:: It doesn't have to be a headlight. Any bulb with a FILAMENT is susceptible. Filaments get brittle with use and time. Bulbs, as mentioned, have a life span in hours. Current changes affect the filaments. When one burns out, there is a SLIGHT current change. When a bulb is new/flexible, those current changes do not affect it much. With a finite life span, the old/brittle filament will fail. This is not BS. Mechanics & electricians, who are not trying to sell me anything, have told me this. I have noticed over the years, the bulbs in my vehicles with less electrical equipment,(ie power window/seats), last longer. My 13 year old truck, with 140k+ miles, has had one brake light burn out. (manual transmission, windows, and locks) I replaced both brake bulbs knowing the other would be failing soon. And they come in pairs anyway. LEDs will last long; no filament.

 

[tuonodave]

As the others have said replace the bulbs in pairs. When it comes to light bulbs especially high output ones the higher the output the shorter the lifespan even the high quality ones. Next time your in the auto parts store look at the back of a set of Sylvania light bulbs. They have a chart showing all the bulb options (halogen, silver star, silver star ultra, silver star zXe) each step up in brightness is a step down in expected life. I usually get about 1 year life out of a quality high output bulb on a frequently ridden bike. To me the trade off of shorter life is worth the increased illumination. I usually put the old stock bulbs in the new bulbs packaging along with the receipt in a baggie under my seat or in my top box for emergency purposes. I have had a few replaced under warranty if less than 1 year old.

 

[2daMax]

The observation:

The theory of if 1 bulb is blown, the other will get be blown also in a short time is only true if both the bulbs are of the same age and gone through the same environment (vibes, etc). That is, they have reached their life expectancy.

I am one of those that did not received the wire harness recall, so I have 1 intermittent connector that causes 1 bulb to be off, while the other is On. I had these symptoms quite a while and only noticed 1 bulb is working when I am following a car and saw the situation via the reflection. Hardly ride at night. So you have it here, it is not true that when 1 bulb is off, the other will work harder and causes it to malfunction. (I kept the original wire harness and switched to LEDs now).

The theory.
The filaments is a resistance, an electrical load. This load is constant unless its resistance change. The load will only draw current as much as it allows through the resistance (resistance impedes current flow) from the power supply. Put in a higher capacity power supply (rated voltage) will not put in more current through the resistance. there is a chance that with 1 bulb is off, the voltage of the system rises. The R/R ensures it is at a safe 14.x level, safe for the filaments. It may increase but probably by 0.2V with 1 bulb being off.

On the comparatively short lifespan of the H7 Halogens in the S10 versus other bikes. I think it is the design of the headlamp housing, which have all the wiring inside a closed container, that exposes the bulbs to a greater heat because the heat cannot dissipate easily. Compared to the Versys, which also uses H7, the connectors are external, and those H7 never burn out in 4 years of usage. Hotter filaments makes the metal softer (reduced mechanical strength) and with vibrations, the cyclic stress leads to fatigue failures.

 

[RhodeTrip]

Correct me if I am wrong, but the bulbs will take whatever they can get within the limits of what they were designed for, and an adequate supply of juice. As long as you are under the amp limit of the fuse, this bike will provide whatever the bulb(s) want. So my reasoning is, after a loss of a bulb the other (it should be close if put in the same time) may go soon as it may initially get that .0000* more due to the other being out when initially turned on, which may be enough to push it over the edge. Also I would think the vibrations or rough road would affect them simultaneously, giving them similar life.

The one bulb out and now the other being brighter would be to me, either perception, or the electrical system is not providing what is really needed with both on.

Mark

Ohms law defines what will happen; current = volts/ohms volts and resistance (ohms ) should be fixed so the current should remain the same. If the lamps burned brighter the most probable reason is the second lamp was on it’s way out and the resistance changed; these lamps pose such a small load to the electrical system that they should not influence the voltage.
Jim

 

[Checkswrecks]

I've been examining bulb failures for a long time and teach about it as part of accident investigations. Both sides are right, but much more the aging argument.


The short version is that tungsten filaments definitely age and when one is reaching the end of it's life, then other will probably go before long. The way they age is a microscopic notching and oxidation process of the tungsten filament surface, which creates a lot of microscopic sharp stress risers and there is also a bit of higher resistance. We use the stress risers to vaguely see how old a bulb is and the stress risers alone can kill the bulb, especially in a use where they are vibrated and occasionally take a bump like a motorcycle.


But since resistance times current makes heat, increased current will hasten how fast those aged characteristics kill a bulb. Electrical power quality (noise) also comes into play. But usually just the loss of one bulb is not enough of a current pulse to kill the other.

 

[Checkswrecks]

On a related note about burning out headlights way too fast, we have a 2013 Subaru Forester. Those and the Outbacks are renown for killing headlight bulbs and I wish I had an o-scope available to look at how much noise is in the electric system of that car.

 

[2daMax]

On a related note about burning out headlights way too fast, we have a 2013 Subaru Forester. Those and the Outbacks are renown for killing headlight bulbs and I wish I had an o-scope available to look at how much noise is in the electric system of that car.

Interestingly on electrical harmonics that may shorten filament's life. I know that they shorten insulation life of cables that powers Variable speed drives or inverters, maybe due to the quick heat cycles that the insulation material doesn't like, sort of a fatigue of rubber polymers.

I may think that the R/R maybe over juicing the system, rather than electrical noise as most noise would come from power transistors switching on and off in the digital circuit. Secondly, heat. Is the reflector housing somewhat has lesser mass or material where it would not dissipate away the heat from the bulbs?

Nevertheless, if you get a chance to scope and log the data, perform a FFT and check the spectrum to see which is the dominant frequency and design in a band pass filter to remove that damaging frequency band. (Filter circuit hooked up to each light bulb). I still don't think this is the cause. Thinking more on higher heat experienced on the filaments. Are those bulbs concealed in the housing just like the S10 or its connectors are outside of the housing?

 

[Checkswrecks]

Interestingly on electrical harmonics that may shorten filament's life. I know that they shorten insulation life of cables that powers Variable speed drives or inverters, maybe due to the quick heat cycles that the insulation material doesn't like, sort of a fatigue of rubber polymers.

I may think that the R/R maybe over juicing the system, rather than electrical noise as most noise would come from power transistors switching on and off in the digital circuit. Secondly, heat. Is the reflector housing somewhat has lesser mass or material where it would not dissipate away the heat from the bulbs?

Nevertheless, if you get a chance to scope and log the data, perform a FFT and check the spectrum to see which is the dominant frequency and design in a band pass filter to remove that damaging frequency band. (Filter circuit hooked up to each light bulb). I still don't think this is the cause. Thinking more on higher heat experienced on the filaments. Are those bulbs concealed in the housing just like the S10 or its connectors are outside of the housing?

Agreed that it could easily be the regulator and a high charge rate at times. The scope is on the 5th floor at work, so being realistic we'll just keep replacing bulbs. It's just interesting that owners of the model do notice it eating bulbs, so I was noting that the Tenere is not the only vehicle that does.


internet photo of Forester headlight assy

 

[draig126]

Interestingly on electrical harmonics that may shorten filament's life. I know that they shorten insulation life of cables that powers Variable speed drives or inverters, maybe due to the quick heat cycles that the insulation material doesn't like, sort of a fatigue of rubber polymers.

I may think that the R/R maybe over juicing the system, rather than electrical noise as most noise would come from power transistors switching on and off in the digital circuit. Secondly, heat. Is the reflector housing somewhat has lesser mass or material where it would not dissipate away the heat from the bulbs?

Nevertheless, if you get a chance to scope and log the data, perform a FFT and check the spectrum to see which is the dominant frequency and design in a band pass filter to remove that damaging frequency band. (Filter circuit hooked up to each light bulb). I still don't think this is the cause. Thinking more on higher heat experienced on the filaments. Are those bulbs concealed in the housing just like the S10 or its connectors are outside of the housing?

One of the causes for shortened insulation life with the use of inverters, ballast, CCFL inverters, and other high voltage and high dv/dt systems is that the corona ionizes the air surrounding and trapped in the minute imperfections of the insulation. This mechanism contributes to the generation of ozone and acids that breakdown of the insulation.

I do agree and was thinking myself that the construction of the headlamp assembly could lead to pre-mature failure and excessive heat could lead to an early failure but I was also thinking that even if the headlamp assembly creates a noticeably higher ambient temperature (compared to other assemblies) that increase would be a relatively small percentage of the temperature which the lamp's element operates at.

If it is the charging system, you may find the issue more systemic with other vehicles from Subaru and other companies they share technology and parts with. I would imagine the same components are used in many vehicles.

Premature failure can be a multitude of contributors and don't underestimate the mechanics of the system. Depending on how everything is hung in the vehicle and the bulbs secured, you may find that the system has a mechanical resonant frequency, granted it may not be resonating all the time but each impact, like hitting a pot-hole or bump in the road, rings the bell (so to speak) and some systems dampen that impact better than others.

 

[hogmolly]

Voltage can be a lifetime killer. A bulb at 13.5V will last much longer than one at 14V.

 

[draig126]

Hogmolly, you are absolutely correct.

If it is high voltage, even in short bursts slowly degrading the bulb, I would guess that the problem may follow vehicles with the same charging / regulator system as the Forester, if that were the root cause.

 

[hogmolly]

I use a GPS on my bike that also displays voltage. It surprises me that it often shows a high of 14.5V and bounces between maybe 13.6V and 14.5V. That's gonna kill those H7 much faster than the packages claim. I will probably just change both at the start of each season in the comfort of my shop and not out on the road.

 

[2daMax]

One of the causes for shortened insulation life with the use of inverters, ballast, CCFL inverters, and other high voltage and high dv/dt systems is that the corona ionizes the air surrounding and trapped in the minute imperfections of the insulation. This mechanism contributes to the generation of ozone and acids that breakdown of the insulation.

I do agree and was thinking myself that the construction of the headlamp assembly could lead to pre-mature failure and excessive heat could lead to an early failure but I was also thinking that even if the headlamp assembly creates a noticeably higher ambient temperature (compared to other assemblies) that increase would be a relatively small percentage of the temperature which the lamp's element operates at.

If it is the charging system, you may find the issue more systemic with other vehicles from Subaru and other companies they share technology and parts with. I would imagine the same components are used in many vehicles.

Premature failure can be a multitude of contributors and don't underestimate the mechanics of the system. Depending on how everything is hung in the vehicle and the bulbs secured, you may find that the system has a mechanical resonant frequency, granted it may not be resonating all the time but each impact, like hitting a pot-hole or bump in the road, rings the bell (so to speak) and some systems dampen that impact better than others.

I like your answers and explanations.

 

[2daMax]

I use a GPS on my bike that also displays voltage. It surprises me that it often shows a high of 14.5V and bounces between maybe 13.6V and 14.5V. That's gonna kill those H7 much faster than the packages claim. I will probably just change both at the start of each season in the comfort of my shop and not out on the road.

14.5V, that is high. I never saw this value on mine before. Mine at highest was at 14.4V and that was after I changed to LED H7. With stock head lamps, it is 14.1V. All at idle speed. When I turned on the LED spot lights, it reads 13.9V at idle.

 

[WJBertrand]

I use a GPS on my bike that also displays voltage. It surprises me that it often shows a high of 14.5V and bounces between maybe 13.6V and 14.5V. That's gonna kill those H7 much faster than the packages claim. I will probably just change both at the start of each season in the comfort of my shop and not out on the road.

Unless your GPS is directly connected to the battery, the voltage variation you are seeing might be due to other accessories on the circuit turning on and off. I have a radar detector (Escort Redline) that reads voltage directly from the battery via my Neutrino Black Box power distribution system and it's pretty steady between 14.3 - 14.5V. Before I fitted the Cyclops LEDs, and using the candle power 65W H7s, voltage would run from 13.9-14.2V, about 0.3V lower on average, but also steady.