Light bulb burns out instantly


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Old 11-24-21, 05:50 PM
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Light bulb burns out instantly

Exterior porch light.
incandescent.
Motion sensor.
Dusk to dawn.
has an override feature so you can turn it on in daylight or leave it on full time.
I came home, light started to come on, then died.
replaced blub. Used override feature to turn it on with the light switch in daylight. Started to come on, then died.
Checked both bulbs in a different light, both dead.
Fixture is old, i dont mind assuming it is the fixture and replace it, but i wanted to check here and see if it could be something else that i should check first.
Dont want to fry a new fixture.
If it could be in the house,i have a meter and i can check voltage, but i dont know where to check because i cant think of anything that would cause a surge ,or short, without tripping the breaker.
Thanks.
 
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Old 11-25-21, 04:14 AM
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You can measure for 120 VAC at the bulb socket if you are careful. Better to get an outlet adapter that screws into the bulb socket. The motion sensor is essentially a switch so there is no way it can increase input voltage. Verify bulbs are rated for 120 VAC.
 
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Old 11-25-21, 05:07 AM
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I have seen this before as bad luck with cheap bulbs.
 
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Old 11-25-21, 06:27 AM
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Did you install or modify any wiring anywhere in the house recently?

Did the fixture with the same kind of bulb work okay before?

Poor quality bulbs burn out quickly because the incoming amperes surge into the filament that has lower resistance at room temperature compared with operating temperature causes something in the bulb to melt.

The most common reason for short life of incandescent bulbs is the voltage is too great. It is all relative. A "long life" (incandescent) bulb is designed for use at, say, 130 to 135 volts giving at 120 volts longer life but less light output per watt compared with a 120 volt rated bulb powered with 120 volts. A 120 volt photoflood bulb is intended to give light at a higher color temperature,has an expected life of about 4 hours at 120 volts, and would give the same light and life at perhaps 90 volts as a 120 volt rated bulb delivers at 120 volts.
 
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Old 11-25-21, 06:41 AM
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Check voltage at the socket with one probe on the screw shell and the other on the center tab. You should read around 120 volts.
 
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Old 11-25-21, 08:31 AM
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Oddly, not uncommon on pre-1940s house wiring. Aka "ghosting".
Not sure exactly why, but quickly flipping lights on causes them to 'pop'.

-Logically, it's oxidation of the switch contacts, which increases resistance and blocks current until there is a breakthrough which sparks across, and can overload old/cheap incandescent bulbs.
-Superstitiously. just call it ghosting, or "shining".

Oddly, it is quite similar to how some people drive down a street or highway, and the streetlights blink-out, or blink-on. I remember driving and somebody was really freaked out by it.
She- "What *^ %^# ^#(( is with all the street lights blinking off?"
Me, "That always happens, I figure it is the headlights tripping some daytime / nighttime sensor."
She- "NO. Nope. I've been up and down this road a thousand times at night, those lights NEVER blink out like that." How are you doing that?"
 
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Old 11-25-21, 12:57 PM
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Bulbs are the same ones i have used for years.
i dont remember when i replaced it last, or when i last bought new bulbs. So i doubt it was caused by cheap bulbs.
This wiring was put in about 1965. I haven't modified anything on this circuit. About half the house is 1930's wiring. That BX with the insulation that crumbles after ,40 years. After time something breaks on those circuits i have to replace the whole run.
i will check the voltage at the fixture.
 
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Old 11-27-21, 07:31 AM
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Typical house switches are cam and spring driven to quickly open/close the two contacts to minimize arcing. Supply voltage at load reaches maximum/minimum in milliseconds when switch closes/opens respectively with resistive (incandescent lamp) loads. There is no way to operate them slower and a operating circuit with only a resistive load can't affect supply voltage.
 
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Old 11-30-21, 12:45 PM
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Incandescent lamps tend to fail at turn on because of the starting current (also called inrush current) being large for a moment. The large inrush current is due to the lower resistance of the lamp filament; the resistance rises and the current drops as the filament heats up and glows.


It is extremely undesirable to create or prolong an arc at turn on to drop the voltage across other components in the circuit and reduce the inrush current. Instead the switch contacts or wherever the arc occurs will be burned and, if there is flammable material nearby, a fire hazard is created..

If the light circuit is equipped with a dimmer, it is perfectly okay to operate the dimmer slowly and this will prolong the life of the bulb (lamp) by eliminating the initial high inrush current.
 
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Old 01-13-22, 06:00 AM
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She- "What *^ %^# ^#(( is with all the street lights blinking off?"
Me, "That always happens, I figure it is the headlights tripping some daytime / nighttime sensor."
She- "NO. Nope. I've been up and down this road a thousand times at night, those lights NEVER blink out like that." How are you doing that?"
Years ago I have once in awhile observed groups of streetlights going on and off repeatedly in a short time or otherwise unexpectedly. There are a variety of reasons, for example several streetlights are on the same "branch circuit" with a single dusk to dawn switch (photocontrol) and a prankster shines a light on the photocontrol to make the lights turn off at night. Nowadays photocontrols are cheap enough that )usually) each light fixture has its own, and streetlights are wired to the nearest 120/240 volt pole transformer without long "streetlight branch circuits."
 
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Old 01-13-22, 07:12 AM
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streetlights going on and off repeatedly in a short time or otherwise unexpectedly
When yellow high pressure sodium (HPS) streetlights start to fail they will cycle on-off in a regular pattern. I once observed that happening at an intersection in Manhattan and it appeared that the street light was being controlled by the traffic lights that cycled every 90 seconds. ​​​​​​​
 
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Old 01-13-22, 08:36 AM
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Try heck continuity of the bulb. I think the photo/switch is bad.
 
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Old 01-13-22, 01:01 PM
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Verify bulbs are rated for 120 VAC.
That made me smile. Decades ago my wife grabbed incandescent bulbs from the shop and took them home. Then she complained they were all bad. I dug one of the sleeves each bulb came in and pointed out that on all 4 sides I had written "12V ONLY". The bulbs were for 12 Volt drop-cords carried on each truck.
 
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Old 01-15-22, 02:17 PM
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Update

I checked the incoming voltage and it was normal.
I decided to just replace the fixture with a new LED since it was so old.
when I took it down I saw corrosion in the socket so maybe that was it. Corrosion shorted the bulb.
whatever, new LED works great.
thanks for the help.
 
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