Normy

What causes light bulbs to burn out?

-Age, of course. The second car that I owned, a 1985 VW Scirocco, had exactly one maintenance issue in the first 40k miles that I drove it: a burned out tail light bulb. That car was a rock!!!

However, the past 24 hours I have been perplexed by a sudden issue that my current 1985 928S2 has developed: It's burning out its left rear parking light.

Now, I've checked the socket- everything seems copacetic [I think I spelled that right-sorry, no dictionary handy], but my Gray-market car's German dashboard keeps saying "Schluss".

Scheisse!

[I think I spelled that correct; My German dictionary doesn't cover profanity!]

Anyway, I can't figure out why a bulb would keep getting fried. My multi-tester says that system voltage is 13.4, which is normal. And I doubt I'm getting voltage spikes- if so, then the other lights around the system would be burning out as well.

Any ideas?

N!

ViribusUnits

Is the seal on the box that the tail light is in good?

Like bulbs burn out when any given spot on the filliment is too small. That thing part gets REALLY hot, and the metal that conducts the current vaporizes. The thinner the metal, the hotter the metal, the faster it vaporizes.

So if the seal is bad, the bulb never comes up to temp, and thus the metal gets deposited on the glass faster, adn the bulb burns out faster.

Normaly, IIRC, part of the vaporized metal is redeposited on the filliment. An equlibrium of sorts. Now, it gets deposited on everything inside the light bulb too. Normaly the bulb gets hot, and that slows the depoiting the metal on the glass. If it gets cold, it deposits it faster, and well, that makes the filliment thinner faster.

Failing that, are you sure the bulb goes out? A bad, or miss connected wire could be causeing the bulb to be on all the time. Stranger things have happened.

ViribusUnits

Oh, another thing, bulbs don't like being viberated. See if the mounting bracket is tightly attached the the car.

Normy

Yeah V, I thought about that. The seal on that rear unit isn't the best- at the same time, I don't notice any moisture in there after I wash it.

Vibration? I've thought of that too, but the bulbs that I've bought over the past 24 hours seem very well mounted. And this car has burned out maybe...2 bulbs in the 5 years that I've owned it.

- I have great eyes. I can read license plates 1/4 mile away sometimes, and can also see [blurry] the end of my nose. The bulbs that are burning out are not burning out at the filament- it appears solid. I can see that the gap in the bulb is occuring at the point where the tungsten winding meets the post.

Thanx again-

N?

ViribusUnits

How many bulbes have you burned out? Over what time peroid?

Another question, are you ABSOUTLY sure they are the right bulbs? And that the bulbs are good?

Maybe time to test a few bulbs from another source?

SharkSkin

Normy, perhaps that lot of bulbs received some high-G shock at some point, which may have fatigued the wire where it connects to the lead in the bulb. Or perhaps that lot is defective due to an irregularity in the spot-welding process. As VU said, try bulbs from another source. Not that there's anything wrong with the brand that you bought(unless they are no-name Wal-Mart specials), but another place may have bulbs from a different lot on their shelves.

HTH

Normy

Well, I've burned three out in 24 hours, and they are all from Auto Zone, a discount auto parts chain on the East coast. The bulbs say they are made in Hungary.

Its conceivable that they are all bad, from a batch that was dropped or somethig.

-Since my 928 was rear-ended [no damage] in 2000, I have used 1156/P21 bulbs in the driving lights position. Most people will tell you that this will cause the plastic to melt and warp, but I've had nothing like this occur.

Could the rear fog light be of some importance?

Here's what happened. Tonight I backed out of a spot, and since there were dozens of people walking around in the lot for some reason, I decided to turn on my Austrian 928's rear fog light...in case pedestrians didn't understand what my roaring Borla/Ott exhaust means [your US model doesn't have this light]. I changed the driving light bulb this afternoon, and then tonight drove across town with no problems. As I was backing up...as soon as I pushed the "Nebelsusschluct" **** [lowest left **** on the pod; on US versions this is the trip-meter reset], the "Schluss" light came on.

-To add to the fire: Jim Doerr has completely replaced all his pod lighting with red LED's. This guy is my hero for interior modifications, so I did exactly what he did and bought 8 red LED's. Only they didn't actually fit- I have good eye-hand coordination, but I still managed to bend all the tabs in the driving light **** when I pulled the bulb and tried to install the LED. I managed to get the LED installed, but when I turned the key and pushed the ****, a whiff of white smoke emerged and then the **** froze! Tomorrow, I journey to a junkyard east of Orlando and attempt to get a replacement driving light switch from my personal "parts-hog" [Rez knows about it too; if he took my switch I'm going to kick his ***!] 928 where I sourced my un-cracked pod.

Hmm...I wonder if I have a wiring problem. Can a wiring issue fry bulbs this way?

N!

Nicole

Normy:

I'm not sure, if I should tell you the correct spelling of the German "s#!t" word. I really don't want to encourage you to use it...

Normy

I knew you would say that Nicole!

"Hoffman912" has already set me straight on the other channel [Off Topic; I cross-posted this time]. I'll fix my mistake, but only because of him. I knew you wouldn't actually spell that. You're too sweet!

N!

SharkSkin

Normy, it's pretty unlikely that the wiring is blowing out the bulb. Sure, there are some inductive loads that feed back into the system, like the AC clutch, the coil(s), etc. Even the coils on the relays do so to some extent. If this is happening it's a transient and you're not going to catch it except with an oscilloscope, preferably a DSO. In any case such transients tend to be short and weak and are generally not going to cause this issue.

If you had another drain on that circuit such as a melting switch, the bulb might try to draw more current, which could be the ol' camel-killer straw.

Feeling adventurous? Slap one of those Auto-Zoned bulbs in the other side and see what happens. Though if they both blow at the same time it may not trigger the warning.

Now, I'm not quite going to say that AZ bulbs might as well be from Wal-Mart... not exactly... um, well, too late. But seriously see if you can lay your hands on some Osram or Phillips bulbs.

OBTW, from a "less sweet" perspective perhaps... http://ets.freetranslation.com/ has it as "Scheiße"... Sorry to be a schmerz Nicole... but IMHO my shark behaves better when I curse at it in German, even pidgin-German. I encourage all DIYers to try it at least once. For example... inaccessible screw... "Ach, der schweinhund putten das schraube unter den gottdamn leichten tvister... dummkopf!

Normy

I love it Dave! Go to it!

N!

ViribusUnits

Mine reacts poorly to cuss words. When I'm all smiles, and praise, and ohs, and ahs, not only asm I in a better mood, BUT the car behaves SO much better.

I think the PO was full of cuss words, and thats what wrong with her now.

Try my methoid. Sometimes it works.

Nicole

Viribus: That mighit be your German pronounciation - the shark just does not understand German with a Texan accent!!! --- just kidding!

Dave: LOL - never heard of "pidgin-German" before. Now, if I could only decipher what you were trying to say there... There was a screw that some stupid son-of-a-b!%&# put under a god d@#ned light 'what'? Maybe I have to refresh my German! Actually I just today practiced a little with my Dad... no swear words, though.

Normy: No harm done. Actually, I admint there ARE situations where I do use swear words, too... was just trying to give you a little bit of a hard time!

jserio

Hey Normy, Just for the heck of it the next buld put with rubber or some type of glove. I kmocked a couple of buls out from the oils on amy hands. Now I never touch any bulb with bare hands. Just my 2 cents.

SharkSkin

Well, I admit, I cheated. I used that translation site for some of the words I was unsure of. "pidgin-language" is an old, old idiom, I don't know the origin. But basically it means that you are speaking a language so badly that huge, often funny errors in grammer and vocabulary are made, yet the message is conveyed.

You got it right, up to "tvister" which is simply "twister" with a german accent.

VB, I talk nice to my shark when it's nice to me. When it's not.... well, let's just say we understand each other.

Here is an actual example of my made-up pidgin-german from my "Knacker Job" page, followed by a picture of the screw that inspired it... basically I am saying "This is f'd up, the mechanical engineer that did this must have been drunk and stupid":

"Ach, das is ge****en, das schweinhund springenwerk engineeren das dummkopf oktoberfestin getrunken poppencorken mit der drunkschwagger..."