Flickering Fluorescent Fixture

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Dear NH,
I have a couple of questions concerning fluorescent fixtures. First, how can you tell with a flickering or slow starting florescent light fixture whether to replace the lamp, replace the starter, or simply get a ladder and twist the tube? If the lamp has no starter but both tubes are misbehaving the same, is the problem both bulbs, the ballast (ouch!) or something else?
EN from Washington, D.C.

Generally speaking, a flickering fluorescent bulb means that one of the pair of bulbs in the fixture has bought the farm. My philosophy of sensible repair is to always replace both tubes. Fluorescent tubes have such a long life and are so inexpensive that it makes sense. Not that it's the most economical solution... it is just a practical viewpoint from someone who has been paid to do this type of work for others. To receive a second call in a month because the other of the two bulbs has gone bad is neither desirable from the customer's point of view ($$) or mine (pride in a job done right).

Fluorescent tubes do not yield themselves to direct testing with a multimeter. So for the handyperson, the only way to test them is to install them in another fixture that you know functions. If you have a 4-tube fluorescent fixture, this is easy... remove one of the still-working pair of fluorescent tubes and replace it with each of the questionable tubes, one at a time. 99% of the time it will be one of the tubes that is the culprit.

However, if both tubes are functional, the problem is with the ballast or starter. The starter is replaced first, and if that does not solve the problem, the ballast should be replaced.

And a special note for the uninitiated... don't spend all day looking for a starter in your fixture! Most modern fluorescent fixtures do not have starters, so if it is not "in your face" (it looks like a small gray cylinder) your fixture don't have one. They are never hidden, though they may be concealed slightly by the tubes.

If you want some good technical information of testing ballasts, the most complete source I have found on-line is The Lighting Center, at http://www.thelightingcenter.com/lcenter/technica.htm.


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