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Light Bulb Socket Troubleshooting

By: Jonathan Z. Kremer

The following scenario happens all too often: someone has a light fixture with an incandescent light bulb. After many months of service the bulb burns out. The bulb is replaced, but the fixture still is not working. The bulb is checked in another fixture to make sure it works, and the connections are examined to see if there isn't a break in the line. All seems to be ok. Sound familiar? So what is happening?

Part of the problem are the many cheaply made light sockets found here in Israel. Some have a thread that doesn't seem to fit the bulbs, making them hard to screw in. This in itself can cause the bulb not to make good contact, causing it to flicker or not work at all. This can also cause the bulb to burn out prematurely. Many sockets don't have a spring under the bottom tab to help with the contact to the bulb.

Never-the-less, I still find that the #1 cause for the above scenario is to be found further inside the bulb socket. The bulb needs to make contact at two points in order for it to work (see fig 1)- at the end (nipple) and on the threads of the bulb. Sometimes the "nipple" on one bulb is slightly bigger than the next. So when a bulb burns out and is replaced, the second bulb doesn't quite make the connection because the first bulb pushed the metal tab too far in (partly due to the bad design of the bulb socket).

Over tightening the bulb can also cause the same problem. This can be seen in figs 2 - 4. Tighten the bulb just enough to make contact and then another quarter of a turn.


Fig 1 - Parts of the bulb and socket


Fig 2 - Bulb in place


Fig 3 - Metal tab pushed in


Fig 4 - Bulb not making contact

This can be remedied by first making sure the electricity is off, and then pulling out the inside tab slightly with a very small screwdriver. This will permit the bulb to make proper contact.

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