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phemens's avatar
phemens
Explorer
Oct 26, 2017

Weird interior light issue

I’m trying to replace a few of the standard 12v dome lights in the bedroom with some LED spotlights I purchased on Amazon. The dome light works, but when I wire in the new light I get nothing. I tested the new light on a 9v battery and it works. Any ideas? I’m not exactly an electrical wizard, but I thought I knew my way around a 12v system, but clearly I’m missing something here...
  • phemens's avatar
    phemens
    Explorer
    Oct 26, 2017
    Maybe it wasn’t clear enough in the OP, but I’m replacing the fixture, not the bulb. Wires are confirmed hot, no popped fuses. The reason I mentioned the 9v battery is that I hooked it up to the new fixture and it works fine, so thus polarity ok
    Mr.Wizard, your issue sounds pretty much like what I’m facing. Guess I can pull a couple of 12v lines for the spotlights?
  • mike-s's avatar
    mike-s
    Explorer
    Oct 26, 2017
    This would be much easier to solve if you told us what type of bulb you're replacing. With the common 921 wedge based bulbs, you can put the bulb in two ways, reversing the polarity. With a bayonet based bulb, you can't always do that - you may have to rewire the fixture.
  • fj12ryder's avatar
    fj12ryder
    Explorer III
    Oct 26, 2017
    phemens wrote:
    Already tried that, polarity is correct, I tried it with a 9v battery as mentioned.
    I'm not sure what the 9V battery has to do with polarity. Did you check the polarity of the socket?
  • MrWizard's avatar
    MrWizard
    Moderator
    Oct 26, 2017
    which lights

    i have run into the same problem
    with lights that have (2) contacts on the bottom
    with incandescent, it seems both contacts are for 'hot' and the case is ground

    for the LED version, one contact is hot the other ground, and the case is NOT used
    so when inserted in the socket it sees too hots, no ground and does not come on
  • ScottG's avatar
    ScottG
    Nomad
    Oct 26, 2017
    Verify 12V is still present at the existing wires. You may have popped a fuse.
    If voltage is still there then reverse the connection of the new light.
  • phemens's avatar
    phemens
    Explorer
    Oct 26, 2017
    Already tried that, polarity is correct, I tried it with a 9v battery as mentioned.
  • DiskDoctr's avatar
    DiskDoctr
    Explorer
    Oct 26, 2017
    Reverse the wiring on the LED unit. It's a common problem. They will only light one way, so no risk. Light Emitting DIODE (= one way resistor)
  • fj12ryder's avatar
    fj12ryder
    Explorer III
    Oct 26, 2017
    Make sure the polarity is correct. The LED won't work if the polarity is wrong.

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