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There are four kitchen ceiling lights with single switch. They fit 4 pin CFL bulbs. Only one of the 4 working. Tested with the new bulbs. Why only one works though all 4 has same switch? Thank you.

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  • Have you done any investigation? There are multiple reasons this could occur, starting with bad fixtures. You'll want to test for voltage at the box connections.
    – isherwood
    Nov 5, 2017 at 14:31
  • Hello, and welcome to Stack Exchange. When did this start happening; upon installation, or afterwards? If afterwards, did they all fail at the same time? Nov 5, 2017 at 14:36
  • About 10 yrs old, happened one by one.
    – Prai
    Nov 6, 2017 at 15:27
  • Thank you, looks its ballast needs replacement or change to LED.
    – Prai
    Nov 6, 2017 at 15:27

2 Answers 2

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Your type of fixture uses a Compact Fluorescent Light with replaceable tubes separate from the ballast.

Most likely, your builder fit "builder grade" (i.e. cheapie) CFL fixtures with cheap ballasts. It's not unusual for several cheapies installed together to fail one at a time within months of each other.

A fixture is made up of 4 parts: the tube, the ballast, the lamp socket, and everything else. Generally cheapies are cheap through and through, but the #1 thing to fail is ballasts, and you can obtain and swap ballasts. Aftermarket ballasts tend to be better made, top brands are GE, Philips/Advance, Osram/Sylvania.

Another option is to switch to LED fixtures and there are two ways to do that.

  • Get a true LED fixture which does not have removable bulbs. There's no need for LED emitters to be changeable, since they will outlive every other component including the house. Quality matters because if the onboard power supply fails, that kills the fixture. Don't buy these at big-box stores, visit 2-3 genuine lighting supply houses.

  • Modify the fixtures with a socket that can take a screw-in LED. However this is not to be done lightly: the fixtures are simply not built for the heat of incandescent bulbs, and can burn your house down if you cheated an Incandescent bulb in there. Unfortunately if there is a socket that can take an incandescent, some goober will put one there. So you cannot use a socket for which incandescent bulbs exist, and this limits you to things like Gu24 or Gu10.

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  • Thank you, looks its ballast needs replacement or change to LED.
    – Prai
    Nov 6, 2017 at 15:26
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4 pin CFL lamps have ballasts, there are quite a few possibilities that could cause the lamps not to light. First failed lamps, if you swap the working lamp with a failed one and now the same lamp in the new position works you need to replace the lamps (I would get 4 as the last one is probably close to end of life). After swapping lamps if neither lamp lights the ballast in that position is probably bad. Most of the fixtures I have worked on have individual ballast for the compact plug in type. If you move the working lamp around this method should help you troubleshoot all of the locations.

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  • Thank you, looks its ballast needs replacement or change to LED.
    – Prai
    Nov 6, 2017 at 15:26

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