headlight failure (H7)

Well, I actually did something about it this weekend. This is what I measured/did:
With 2002 XG350 running: V battery = 14.2 v V at headlight = 13.43 v
V headlight + to battery - = 13.55 v
This tells me there is a 0.12 volt drop in the ground wiring (seems reasonable), and a 0.65 volt drop in the positive side which probably includes wiring, a fuse, and a switch of some sort (relay, transistor, or both).
So I placed a 10 amp diode in the passenger side headlight circuit. It now reads 12.8v (headlight + to battery -). This should imply that the voltage measured at the headlight is now around 12.68v (I did not measure this). As I installed the diode and placed it in and out of circuit while watching the headlight intensity, you could tell the difference, but only because you had the 2 to compare. Its virtually impossible to tell by looking now that the passenger side headlight is a little dimmer than the driver side. My plans are to run this for a week or two and then install a diode on the drivers side. I will then see how long it takes to burn out a headlight or two. If they still burn out in under 3 months I might try a second diode in each side - which should drop the voltage at the headlight down to right around 12.0 volts.
I'll post updates as they occur.
Dan
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Good stuff Dan. Thanks for posting this. Why bother waiting a week though? That won't really show you anything, so why not just go ahead and install the second diode now and start the clock ticking?
-Mike-
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for some strange reason, it would not take out both headlights. As soon as I convince myself that this is a stable configuration, through multiple startup - drive - turn off cycles and a number of hours of run time, then I'll go ahead and do the other side. What could possibly go wrong with a simple diode I hear you ask? I've been an engineer too long and seen too many instances of the impossible happening to ever ask that question "what could possibly go wrong?"
Dan
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OK wait a second, how many watts is the bulb? Low AND high beam... let me know and I'll try to help here. using load and voltage we could calculate the watts load on the diode. You have apparently overheated the diode. But don't forget there are industrial diodes that can take the heat, heat sink included, chassis mount or stud mount. You have a good idea, just need better hardware. Also industrial voltage regulators. cheap if the bulbs go out every 3 months! Interesting project, can't wait to see how it turns out.
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will be about 1 V or less and install them in series until you get 12 volts. measure across the filament for 12 Volts. or use a Zeener 10W diode for example a 1.5V zeener will give you almost exactly what you need, they come in all different available voltages, such as 2 volt, 1.5 Volt, 1.8 volt.... some are stud mount for more secure mounting. that would be recommended. OK make sure it's an isolated stud. Yes any electrical circuit has a voltage drop, thats normal. Well halogen lights are well known for short life, over-voltage won't help that's for sure. But a good alternator shop can adjust the output voltage easily. you might as well install diodes to get 12volts on both sides now. you are right, over-voltage will fry the filaments, no question. That's funny, the headlights on my accent have lasted 70,000 miles, 5 years. why won't Hyundai do something to fix the bug? Is there Xenon replacements?
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Snip
pardon my question, if it has been answered in earier posts, but is the voltage at the lamp known to be abnormal-too high? If every other of the 1000's of like cars and bulbs are at that figure, maybe heat or vibration or some other thing more unique to your vehicle is the culprit ? Good luck !
(as an aside, I've changed one headlamp in 2 yrs/60k mi, 06 sonata)
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of Hyundai cars out there with H7 bulbs that go through them like popcorn. I own two XG350's (his and hers) that both have had the alternator replaced once, so that's 4 alternators and the H7 bulbs seem to last 6 months if we are REAL lucky. So if its an over voltage problem, I suspect its a design flaw and not due to a failed piece of hardware. I'm use to the old cars that needed a new set of headlights once in their entire life (of coarse that was only 100,000 miles)...You never thought to buy a spare headlight...with the H7's I wouldn't dream of going anywhere without a couple spare bulbs in the trunk!
So, anyway, this is a first attempt to see if a lower voltage will fix the problem.
Dan
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This is a multi-part message in MIME format. --------------060908020808010407090102 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit
Dan K wrote:

</pre> <blockquote type="cite"> <pre wrap="">Well, I actually did something about it this weekend. This is what I measured/did:
With 2002 XG350 running: V battery = 14.2 v V at headlight = 13.43 v V headlight + to battery - = 13.55 v
This tells me there is a 0.12 volt drop in the ground wiring (seems reasonable), and a 0.65 volt drop in the positive side which probably includes wiring, a fuse, and a switch of some sort (relay, transistor, or both).
So I placed a 10 amp diode in the passenger side headlight circuit. It now reads 12.8v (headlight + to battery -). </pre> </blockquote> <pre wrap=""> Snip
pardon my question, if it has been answered in earier posts, but is the voltage at the lamp known to be abnormal-too high? If every other of the 1000's of like cars and bulbs are at that figure, maybe heat or vibration or some other thing more unique to your vehicle is the culprit ? Good luck !
(as an aside, I've changed one headlamp in 2 yrs/60k mi, 06 sonata)
</pre> </blockquote> <pre wrap=""><!---->That's just it, nobody knows for sure what the problem is. There are a lot of Hyundai cars out there with H7 bulbs that go through them like popcorn. I own two XG350's (his and hers) that both have had the alternator replaced once, so that's 4 alternators and the H7 bulbs seem to last 6 months if we are REAL lucky. So if its an over voltage problem, I suspect its a design flaw and not due to a failed piece of hardware. I'm use to the old cars that needed a new set of headlights once in their entire life (of coarse that was only 100,000 miles)...You never thought to buy a spare headlight...with the H7's I wouldn't dream of going anywhere without a couple spare bulbs in the trunk!
So, anyway, this is a first attempt to see if a lower voltage will fix the problem.
Dan </pre> </blockquote> One thing to remember, while we usually use the term 12V battery, it really means 12.6V, no-load voltage battery. That's the normal voltage for a fully charged lead-acid battery under NO-load condition.<br> With the car running, the alternator has to provide a higher voltage to recharge the battery, so the voltage should be 14.4V plus or minus 0.4V depending of the load.<br> The bulbs manufacturers take this into account.<br> For what you measure, your car is at the low-level of the range, so over-voltage does NOT seem to be the problem.<br> Have you tried another brand of bulbs ???.<br> BTW, Elantra GTS 02, Santa Fe LX 03, both still original lamps .... so no, I do not have any problem.<br> </body> </html>
--------------060908020808010407090102--
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The voltage is okay in this case (14.2V). That's normal alternator output. In my opinion, the culprit is the H7 bulb itself. For whatever reason, it seems to burn out quickly.
Dan's theory, however, is that if we reduce the voltage to the bulb but still keep it high enough for proper lighting, bulb life may be significantly increased. Hopefully, he'll report back when he's been able to conclude something.
-- Message posted using http://www.talkaboutautos.com/group/alt.autos.hyundai / More information at http://www.talkaboutautos.com/faq.html
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I used to have these halogen headlight bulbs burn out very rapidly, until I learned that you cannot touch them with your bare hands when you are installing them, as the natural oils on your fingers will cause them to fail prematurely. I started wearing cotton pallsbearer gloves when I change my headlight bulbs and the early failure problems went away completely.
My .02 cents, ymmv
me On Mon, 17 Mar 2008 16:28:22 -0500, "hyundaitech"

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This is a very well known issue with any high temp bulb. Perhaps there are people who still don't know about it and are handling their bulbs incorrectly, but the real problem is that for the people who do know about it, the problems with H7 bulbs persist. Your bulbs will fail also, unless you've found a brand that is a bit longer-lived, in which case we'd all sure like to know about that.
--

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Mike Marlow wrote:

FWIW, I've had Hella Optilux XP bulbs in my Elantra for over 8 months now, which is longer than any other bulb I've tried.
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Good input Brian. Thanks.
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Mike Marlow wrote:

I'll try to keep everyone updated on these bulbs. So far, so good.
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Although I never checked the voltages across the headlights on my 2001 XG300, the 14.4V or so to the battery on charging sounds like mine. That said I still have the original battery & I have never yet, touch wood, changed a headlight on that car! The only bulbs to burn out have been the licence plate marker & the glove box light. The other consideration here is my car is Canadian & has always had daytime running lights on (all lights on but reduced intensity during day). BCinBC

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For what its worth I work in medical electronics and I never buy any lamp or battery from a certain country. No names mentioned but I,m sure you could guess.(not Korea) I,ve done comparative studies of different brands to justify it. Even Panasonics who used to make excellent batteries shifted manufacturing to this country and now they are just as bad as the others. John

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Well..... that all by itself is useless, unless you tell us where you have found good bulbs.
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