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Florescent light flickers-----after it's been working

Discussion in 'LEDs and Optoelectronics' started by Juliansdad, Jul 27, 2011.

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  1. Juliansdad


    Jul 27, 2011
    I own a ceiling fan with a florescent light fixture at the bottom of the unit. The fixture contains a double circline florescent tube light. I’ve used it on workdays for about 10 months as it hangs above my desk. It’s always worked well…..until a few weeks ago.

    Recently, the light has begun flickering approximately 4 minutes after I’ve turned it on. The flickering is intermittent, but the flickers generally become longer and more frequent as time passes. Sometimes though, this doesn’t occur. The fan still works consistently well. The problem is just the light.

    Is this nothing more than the florescent bulb dying or is there something else that I should examine here?
  2. daddles


    Jun 10, 2011
    The flickering is caused by ragged current flow through the plasma inside the tube. This, in turn, can be caused either by the tube going bad or the electrical circuitry driving it. To my knowledge, there's no easy way to diagnose which one is the cause, although it wouldn't hurt to call a local lighting business; a specialist might be able to give you some hints. The usual thing is to replace the bulb first and, if that doesn't work, then the electrical guts.
  3. shrtrnd


    Jan 15, 2010
    All my worklights over the years have been flourescents.
    daddles said what I would do.
    Replace the bulb, 95% of the time, that's the problem.
    Something I'd think about since this is in a ceiling fan, is to take a good look at the
    lamp socket, to make sure the contacts are making good contact for the new bulb.
    Also make sure any clips holding the lamp in the fixture are making snug contact.
    If the bulb has been wiggling because of vibration due to rotation of the fan, it might
    cause the bulb socket contacts to become loose. I've lost a couple of bulbs prematurely
    because of poor electrical contact to the bulb.
    good luck
  4. Resqueline


    Jul 31, 2009
    Does the tube have blackened ends? Is there a separate starter?
  5. daddles


    Jun 10, 2011
    Just FYI, I believe the blackened ends are caused by the evaporation of the tungsten filaments onto the tube (and/or the effects of radiant heating over time, as the filaments get red hot for thermionic emission when starting the tube).
  6. Juliansdad


    Jul 27, 2011
    Great suggestions, ladies and gentlemen. Thanks. I bought a new bulb today and installed it, paying attention to the contact. For 10 minutes, everything was fine and I assumed that the new bulb solved the problem.

    I left the light on and I left the room for about a half hour. When I returned, the light was flickering rapidly, almost like a strobe light. :(:(

    Where would you go with this issue to resolve it now? I'm having an electrician here to install a chandelier in another room. Is there any particular test that I should ask him to perform on this light while he's here?

  7. daddles


    Jun 10, 2011
    Another cause for flickering is when you're using a bulb that's not properly rated for the fixture you're using. So make sure you bought the correct bulb (and that the original one you had was correct).

    If it isn't the bulb, then the starter/running circuit is suspect. Unfortunately, there's no easy way to troubleshoot these unless you have the schematic and electrical knowledge. Then you may be faced with taking the fan/light into a lighting store and have them try to fix it for you.
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Yeah, have the light on and flickering for him to look at. Then show him the old bulb ("Mr Electrician, I changed this") and see if he can figure it out.
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