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:
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.
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.
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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.
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.
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
Huh?
How did they fail?
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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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.
Vibration, shock.
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
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
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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.
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
For years now I use Deoxit to clean the socket then apply DC-4 grease when I replace the bulb. This seems to be especially benifical on my camper and boat trailer lights and trailer connections.
Jimmie
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 say, that`s rather a generalisation. Many halogen lamps are designed to be run at any precentage, theatre lighting for example.
Ron(UK)
I prefer to be the master of my lighting. If that means changing a bulb occasionally, so be it.
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