Reply by WoodKutter

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Posted on fluorescent light questions

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29 posts in 3436 days

#1 posted 10-04-2012 09:47 PM

Jesse, The light fixtures you have are quite old. The T12 ballasts in them generate a lot of heat. The black ends of the bulbs are caused by the heat generated in the fluctuations of current caused by the old ballasts. It will cause the bulbs to burn out prematurely. The fixtures on which you moved the bulbs or took out and put back in for them to work have weak ballasts. The ballasts are not putting out enough to fire up the bulbs. By moving them, you cause an arc at the lampend which spikes the current slightly. Once the bulb lights up, it takes very little to keep it lit. The fixtures which come on and go off sporadically have ballasts which are dying. They over heat, shut down, cool off, come back on. They may stay off for days, then one day start working again for a few days. Sometimes they strobe and drive you crazy.

The problem you will have with updating those old fixtures to T8 ballasts and bulbs is that the wiring colors are different. The T12 ballasts will have 2 yellow wires, 2 blue wires and 2 red wires. The T8 ballast will have 1 red wire and 2 blue wires. Also you may have to change the wiring in the fixture. Some T12 40watt ballasts are wired in series and some are wired in parallel. It is not hard to do but you need someone who knows how. A lot of times the wire insulation is brittle and will break when moved. If you know someone who can show you what to do on one fixture, you can probably do the rest yourself.

My advise would be to replace the entire fixture with a new one. Often times you can buy a whole fixture for about the same or less than the cost of a ballast. The ballast went out in my kitchen light and I purchased a new fixture for about $10 dollars more than the ballast by itself. And it was a nicer light fixture than the one I had.

Good Luck,

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