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Premature failure of light bulbs


Have you ever had a certain light fixture in your home where light bulbs constantly burn out? I do, and this is a newer home built in 2003, so I went looking for an answer. As a prior electrician I was thinking about all kinds of things like loose grounds or neutrals, overvoltage, etc… But a quick Google search revealed that it just might be the nut behind the keyboard (me). One post revealed that screwing in the light bulb too tight will deform the middle conductor in the fixture and cause a poor connection. This could result in mini arcs of electricity which essentially turn the bulb off and on causing a shortened lifespan.

I’ve had failing light bulbs in many of the recessed fixtures in my home. By failing I mean within hours to days to a couple weeks! These occurred in the upstairs hallway and above the kitchen sink. A few months ago I tried the trick with the hallway lights and they are working great now. Today I tackled the light above the sink, taking pictures as I went so I could share this information with all my friends.

The theory is that when a person screws the light bulb in to far the center conductor in the fixture gets bent down and doesn’t make good contact with the light bulb. I’m thinking this wasn’t a problem in the past because light bulbs of old had very large center conductors compared with those we get now due to the manufacturers putting much less solder on the end. Here is a picture of a modern light bulb center conductor.

Yes, it’s blurry but you can see that the solder (silver stuff) doesn’t cover much area. So I remove the old light bulb and take a look in the socket. I’m amazed and how deformed the center conductor is. There is a recessed hole at the center that the conductor has been pushed into and it won’t return to its normal position on its own. Here is a picture of the fixture.

Of course the standard safety warning; do NOT put anything into the socket until you make absolutely sure there is no power there. I turned off the switch and tested it with a meter. A safer method is to cut power by turning off the circuit breaker. Do NOT blame me if you get a shock! This thing is pushed so far in that I can’t get a grip with needle nose pliers. I’m thinking a dentists pick would work perfect, but alas, I’m not a dentist and have no desire to pursue that line of work. So after a few minutes of standing in the garage thinking, I grab a small 4d box nail and bend the end 90 deg. In retrospect I should have used a finish nail because the head of the box nail hampered its use as a pick using the pliers.

Anyway, I use the nail to pull the center conductor of the fixture back out to where it should be so it will make good contact with the light bulb.

As you can see the contact is now back where it should be. So how do you install a light bulb without crushing the center conductor? Make sure power is on and switch is on. Then screw in the light bulb until it comes on and then go a little bit more; an eighth to a quarter turn. This has worked with the hallway lights perfectly and I expect the same with the light above the sink. Having replaced the incandescent bulbs in the kitchen with CFLs over a year ago, I think the CFLs tend to be more forgiving to over tightening. But I do not like CFLs because of the slow start up to full performance. With the current deadline of 2012 looming for buying certain incandescent light bulbs I’m going to be building up a stock pile. The following years more and more bulbs will be banned. And with this knowledge I’m confident I can rely on them lasting longer than a few days.

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