Premature halogen bulb failure

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These are 40W Wagner 795 halogen bulbs used in an automotive light
bar. They failed prematurely. We were very careful installing them
that they were never touched by hand. So I have some questions:
1. Why is it that touching halogen bulbs can decrease their life? This
is a sealed bulb.
2. Should we clean them with 99% isopropyl before installing them?
3. Does anyone have any ideas as to why these failed prematurely?
Thanks, Lenny.

 

[Charles]

These are 40W Wagner 795 halogen bulbs used in an automotive light
bar. They failed prematurely. We were very careful installing them
that they were never touched by hand. So I have some questions:
1. Why is it that touching halogen bulbs can decrease their life? This
is a sealed bulb.
2. Should we clean them with 99% isopropyl before installing them?
3. Does anyone have any ideas as to why these failed prematurely?

http://www.cast-lighting.com/art-lamp-burnout.html

 

[James Sweet]

These are 40W Wagner 795 halogen bulbs used in an automotive light
bar. They failed prematurely. We were very careful installing them
that they were never touched by hand. So I have some questions:
1. Why is it that touching halogen bulbs can decrease their life? This
is a sealed bulb.
2. Should we clean them with 99% isopropyl before installing them?
3. Does anyone have any ideas as to why these failed prematurely?
Thanks, Lenny.

Finger oils can burn and darken, creating a hot spot on the quartz.

Yes cleaning them would be a good idea.

How prematurely? Lots of things can cause early failure. Defective
manufacturing, poor handling, excessive vibration, excessive voltage, etc.

 

[John Tserkezis]

How prematurely? Lots of things can cause early failure. Defective
manufacturing, poor handling, excessive vibration, excessive voltage, etc.

Remember also that low voltages cause a reduced life span as well.

If they don't run hot enough for the tungsten molecules not to re-deposit
onto the main filament, they may deposit on the inside of the bulb as per with
normal incandescent lamps.

It won't kill it quickly, but will have a significant effect on the life.

 

[Jakthehammer]

These are 40W Wagner 795 halogen bulbs used in an automotive light
bar. They failed prematurely. We were very careful installing them
that they were never touched by hand. So I have some questions:
1. Why is it that touching halogen bulbs can decrease their life? This
is a sealed bulb.
2. Should we clean them with 99% isopropyl before installing them?
3. Does anyone have any ideas as to why these failed prematurely?
Thanks, Lenny.

They got burn out quickly because their over-work, Check its resistance.
Halogen has 0.4 ohm(=load) as supposed to 0.6 ohm=regular bulb. Remember
bulb are designed for 12V not good for above 14V - 15V. If your regulator
Fuse was removed, your Alternator output may not be regulated down to 14,
you may have 15V instead of 14. This would kill the bulb quickly in 1-2
weeks. I had the same problem because my new alternator produce 14.4V, the
solution is to use regular light bulb.

 

[jakdedert]

These are 40W Wagner 795 halogen bulbs used in an automotive light
bar. They failed prematurely. We were very careful installing them
that they were never touched by hand. So I have some questions:
1. Why is it that touching halogen bulbs can decrease their life? This
is a sealed bulb.
2. Should we clean them with 99% isopropyl before installing them?
3. Does anyone have any ideas as to why these failed prematurely?
Thanks, Lenny.

The failure of a halogen bulb from finger oil is only from touching the
actual quartz is pretty immediate. The envelope either cracks...or
better yet, begins to soften at the point of finger contact and swells
like a balloon until it fails.

If you are merely experiencing shorter life than you expected, there
could be any number of reasons. One reference specifies that this lamp
should only be used in horizontal applications and that expected life is
only 200 hours.
<http://www.donsbulbs.com/cgi-bin/r/b.pl/795|12.8v|3.9a~usa.html>
That's not much, compared to most automotive applications. By 'light
bar', I assume you mean some kind of off-road aftermarket auxiliary
lighting installation. That would imply a more rigorous than normal
application, subject to a lot of vibration and shock.

Given a 200 hour rating under 'normal' conditions, I believe this might
be your answer. In any case, it's never a bad idea to clean the
envelope when installing. Many manufacturers supply an alcohol 'wipe'
for the purpose.

jak

 

[James Sweet]

They got burn out quickly because their over-work, Check its resistance.
Halogen has 0.4 ohm(=load) as supposed to 0.6 ohm=regular bulb. Remember
bulb are designed for 12V not good for above 14V - 15V. If your regulator
Fuse was removed, your Alternator output may not be regulated down to 14,
you may have 15V instead of 14. This would kill the bulb quickly in 1-2
weeks. I had the same problem because my new alternator produce 14.4V,
the
solution is to use regular light bulb.

Huh?

 

[Sam Goldwasser]

How did they fail?

Finger oils can burn and darken, creating a hot spot on the quartz.

Yes cleaning them would be a good idea.

How prematurely? Lots of things can cause early failure. Defective
manufacturing, poor handling, excessive vibration, excessive voltage, etc.

Also, there's a range below spec'd power where life will be reduced
since it's not hot enough for the halogen cycle to work properly.

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[PeterD]

Huh?

<g> Me thinks he missed the true solution, which would be to get an
alternator that worked correctly!

Of course who knows where the automotive angle came in.

 

[Meat Plow]

These are 40W Wagner 795 halogen bulbs used in an automotive light
bar. They failed prematurely. We were very careful installing them
that they were never touched by hand. So I have some questions:
1. Why is it that touching halogen bulbs can decrease their life? This
is a sealed bulb.
2. Should we clean them with 99% isopropyl before installing them?
3. Does anyone have any ideas as to why these failed prematurely?
Thanks, Lenny.

Vibration, shock.

 

[Jakthehammer]

Huh?

Huh? Plug a meter in a cigarette lighter, make it solid, drive your car,
and the truth will reveal itself on the meter.

 

[jakdedert]

Huh? Plug a meter in a cigarette lighter, make it solid, drive your car,
and the truth will reveal itself on the meter.

That would assume that *all* the bulbs on the vehicle were failing
prematurely. Since the OP seems only concerned about this particular
one, the odds are pretty small that the alternator is at fault.

The particular lamp to which he refers only has a 200 hour life under
average conditions, which presumably is not the case here.

jak

 

[James Sweet]

Huh? Plug a meter in a cigarette lighter, make it solid, drive your car,
and the truth will reveal itself on the meter.

I'm not the OP, but 0.6 Ohm sounds like the cold filament resistance, which
has little to do with the load of the bulb. If it was really .6 Ohm it would
be over 300W. If halogen bulbs are failing, regular bulbs should fail just
as quick.

 

[jakdedert]

I'm not the OP, but 0.6 Ohm sounds like the cold filament resistance, which
has little to do with the load of the bulb. If it was really .6 Ohm it would
be over 300W. If halogen bulbs are failing, regular bulbs should fail just
as quick.

Provided a link to the specs. It's a 50 watt bulb. The OP hasn't
chimed back in. This thread is dead AFAIC.

jak

 

[[email protected]]

Provided a link to the specs.  It's a 50 watt bulb.  The OP hasn't
chimed back in.  This thread is dead AFAIC.

jak- Hide quoted text -

- Show quoted text -

Sorry that I haven't gotten back to the group on this. It seems that
there are two of these bulbs operated in a VERTICAL position in the
light bar. I don't understand the theory behind the horizontal
recommendation but perhaps thats the cause of the problem. Perhaps I
should chaulk it up to a poor design and just replace them with a
couple of standard tungsten bulbs.Lenny.

 

[Dan K]

I'm beginning to think my premature headlight failures are due to a less
than 100% good electrical connection at the bulb, as I noticed with the last
failure that the connection seemed a little loose. (I've done all the
obvious checks and handling precautions and still go through H7 bulbs like
popcorn). This time I put some electrical conductive greese on the spade
lugs before plugging the light in and its been working fine for a while
now...time will tell.

Dan

 

[CJT]

Halogen lamps are sensitive to reduced voltage, because they have to run at
full temperature for the halogen cycle to work.

For this reason, you should never only slightly dim a halogen lamp. Either
run it at full, or dim it a lot.

I prefer to be the master of my lighting. If that means changing a bulb
occasionally, so be it.

 

[James Sweet]

I say, that`s rather a generalisation. Many halogen lamps are designed to
be run at any precentage, theatre lighting for example.

Aren't they only rated a few tens to a few hundred hours too?