Hope I'm in the right forum here. I'm just Joe Homeowner looking for the answer to a puzzle. I recently replaced my two porch light fixtures using the existing wiring. Now the bulbs blow after only four or five days, and they are lit only from dusk to about 11 p.m. I read somewhere (of course I can't remember the source) that a high-resistance short can be caused from cracked insulation (very likely in this case)and that such a leak would not be enough of a short to trip the breaker but "at the very least you'll burn out your bulbs faster." Am I remembering this correctly? It doesn't make sense to me because wouldn't a short be a decrease in current to the bulb, not an increase? If I'm way off on this high-resistance short theory, any ideas on why I'm suddenly burning bulbs so fast? Thanks for any help.
One of the most common causes of early lamp failure is poor contact between the lamp base and the socket. This can produce enough heat to melt the solder at the base of the lamp and allow air to enter the lamb. Once air is in the lamp it will fail almost instantly. This problem can be caused by not screwing the lamp in tightly or poor quality sockets. What do the burnt out lamps look like? Most of the time if air has entered the lamp you will see some yellow stuff inside the glass. Don(resqcapt19)
Interesting Just yesterday, I noticed my bedroom walk-in closet light fixture was not operating properly. Turn it on, sometimes it works and sometimes doesn't. This is keyless type and has been in the house probably more than 30 years. Well, upon a little investigation, I finally see the little tip down in the bottom has a hole burned in it. So, when I moved the light bulb around, it made contact, but would not maintain contact. The house has an attic fan, and was used many years before we bought the house. We used it a few years, then added central AC. But the vibration of the attic fan would cause the incandescent bulbs to go out very quickly. After central AC was installed, the bulbs lasted much longer. My next step is to replace the fixture, with something a little better than a keyless.
If, as you say it is likely that there is cracked insulation somewhere "(very likely in this case)" I believe that you sould direct your attention to that first by having it looked at by a professional.
Perhaps they could also give you some ideas about the bulb situation while they are there.