This junction box houses electrical wiring to a light fixture in a closet. The light no longer works and i'm wondering if this black thing is a possible cause.enter image description here

  • What type of bulbs does the fixture use? (Incandescent? Fluorescent tubes? Something else?) Jan 5, 2019 at 16:32
  • It uses a standard incandescent bulb, but it has a CFL bulb in the socket. Thanks for reading my post.
    – Rob Beck
    Jan 5, 2019 at 16:41
  • I take it said black cylinder has no labeling of any sort on it? Jan 5, 2019 at 17:01
  • well i haven't taken it out yet, so i'm not sure if it has any tiny print on it or not. i was just curious to know what it was before pursuing it.
    – Rob Beck
    Jan 5, 2019 at 17:11

1 Answer 1


That is an obsolete thermal detector and shut off if the can light gets overheated. It is probably why your can light is not coming on because it has ceased to operate. You can no longer get a replacement since they stopped manufacturing it sometime ago. If you find someone that still has one in stock you can replace it, but I ran out of them years ago so good luck. The only thing that can be done is to install a new can with a new built-in thermal detector. This could be a little complicated and may not be something a DIY could handle since you have to purchase the right part which is not a stock item and rewire the box to make it work properly. Sorry I can't be of much more help.

Good luck and stay safe

  • Thank you so much for that answer! Is a thermal switch really needed? The junction box is right above the light fixture in the attic. Don't know why it would be needed up there and a foot away from the fixture.
    – Rob Beck
    Jan 5, 2019 at 19:38
  • I agree, I have found many fixtures that have failed because the thermal safety failed open.
    – Ed Beal
    Jan 5, 2019 at 19:52
  • Yep, it was the thermal detector that was bad. Thanks all!
    – Rob Beck
    Jan 7, 2019 at 1:49

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