"Scott Badman" wrote in message
...
"Chad Wahls" wrote in message
...

"Scott Badman" wrote in message
...
"DoUbLeStUf" wrote in message
news The halogen headlamps in a motor vehicle function differently to the
incandescent blubs in your home. The halogen bulb is a hive of
activity
with bits of the filament breaking away, then refusing, breaking away,
refusing, etc etc in a continuous cycle.

When the lamp runs under voltage this fusing process doesn't take
place
properly, causing wearing of the filament. Hit the lamp with full
voltage
again, and the deteriorated filament can not handle the current, and
blows.

The constant vibrating forces present on the globe don't help either




I highly doubt the magic composition of halogen lamps in the automotive
environment differ from those used in professional lighting applications
and
homes where they are dimmed all the time. In pro apps the lamps are
almost
NEVER full tilt. I have found them to last longer dimmed. As long as
that
baby is making light this chemical process is happening. I imagine it's
a
fairly linear function. I suspect vibration and voltage overshoot.

Chad



I too know about the life increase with filament globes at reduced
voltages,
it is an inherent part of my job to know this. I also know however that I
ran 130W globes on my car through insufficient wiring for a while, then
after upgrading the wiring they both blew inside of a week!

Hence forming the basis of the only explanation I could think of, even if
it
did go against what I already knew!



This is a long term scenario not short term like momentarily dimming
headlights. Did you get new 130W lamps? Did they do OK?

I just don't buy the fact that by running a lamp under it's specd voltage
will shorten it's life if the specd voltage is applied.

I still go for vibration and voltage overshoot.

Chad