I have ceiling fixtures, let's call them A and B. Normally, both fixtures are always on (lit) -- no switch controls them.

When I remove the bulb from A, fixture B goes out.

Here's how it looks inside the junction box that feeds both fixtures: enter image description here

Fixture A is at the top of the box. Fixture B is the one on the bottom (I think, not 100% sure about that.)

As you can see, the white wire from Fixture A is connected to the other white wires in the junction box. That makes sense.

But, the black wire from Fixture A is jumpered onto a white wire, that's then connected to the white wire on Fixture B.

What's going on here?

I plan to put motion-detector bulbs in both fixtures, so I want them both hot all the time.

Can I just remove that white jumper wire and connect the black wire to the other black wires?

I have confirmed that there's nothing wired downstream from the Fixture A box - the wires terminate there.

  • 1
    If these are 24 hour lights with no switch, my guess is that they were intentionally wired in series to keep them from burning out... That is if they are standard incandescent light bulbs. They will put out much less light each wired in series, but will rarely burn out. What kind of lightbulb is used here? – Tyson May 7 '16 at 3:31

It's difficult to tell for sure, as I'm not sure where all the wires in the box go. But it looks like the lights are run in series, rather than in parallel as they should be.

To fix it.

  1. Turn off the power and verify that it's off.
  2. Connect all the black wires together in one twist-on wire connector.
  3. Connect all the white wire together in the other twist-on wire connector.

This image shows how electricity moves through the circuit.

Power through junction box

Notice that the neutral wire "coming back from" light B connects to the hot wire "going to" light A. Then the neutral "coming back from" A, connects the the other circuit neutrals.

The only way that this wiring would make sense, is if B was a switch controlling A.

removing the bulb from either A or B interrupts the circuit, and causes both light to go out.

  • 2
    Agree with @Tester101 but similar lamps wired in series will each see half the supplied voltage. Check for these conditions: (1) the bulbs were very dim when they were on, (2) the bulbs are rated for 60 volts, (3) this is a 240 volt circuit. – A. I. Breveleri May 6 '16 at 17:21
  • Yes - the bulbs were very dim when on. I have lost one, and can't reach the other right now, but I will check. Thanks for annotating the image @tester101 - that's my understanding of it also. I remember seeing a box up there labeled "240V DANGER!" but I don't remember if this box is hung off of that. I'll check. – Matthew Rechs May 7 '16 at 12:06

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