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I just replaced a broken light fixture in my closet. (The switch in the light fixture broke when I pulled too hard on the chain.)

When replacing the light fixture I noticed that there is only 30 V AC between the white and black wires. The ground wire is cut back and is not being used. By the way, the wiring in my house is all aluminum.

I know the new light fixture works. I checked it out with my multimeter, and I tried it in a different closet. But the light bulb won't turn on because there is only 30 V. (Even if I disconnect the light fixture completely there is still only 30 V.

It seems to me that it must be a problem with the wiring. My attic does provide some (difficult) access to the wiring, but I am not sure where to start looking for the problem or what to look for. Can anyone offer some suggestions?

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    The first thing I would do is take your multimeter and go to another fixture and make sure you see 120VAC on it - just to make sure the meter works correctly (assuming you are in a 120VAC country) – Aaron Jan 18 '13 at 20:41
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    Sounds like you have a bad connection somewhere. This can easily happen with aluminum wiring and is a fire hazard. – BMitch♦ Jan 18 '13 at 22:43
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Are you sure the circuit was live when you measured it? If you try to measure an open (i.e. off) circuit, you can sometimes read a "phantom voltage" caused by coupling with other nearby live wires. Phantom voltages can't generate a significant amount of current and are therefore harmless, but they can be measured by a multimeter.

If you say the fixture doesn't work even though the old one did, perhaps a connection came loose somewhere and now you have an open circuit with only the phantom voltage. Or maybe you just forgot to switch the breaker back on?

I don't see how the old fixture could've worked if it was actually only getting 30 volts, so something must've changed during your installation.

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This can happen if you use a 3-way switch. Lower voltage will cross the travelers.

A "live" circuit will carry the 110, an "off" circuit may carry some lower voltage.

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  • This light isn't on a three way switch. but I will definitely keep this in the back of my mind. – Stainsor Jan 20 '13 at 20:42
  • 30V should, then, be very unlikely in a direct circuit... even with poor connections. Try checking potential from the neutral to ground and see what you get. – Matthew Jan 22 '13 at 17:29
  • Why would an 'off' traveler have voltage on it? – Mazura May 26 '15 at 23:29
  • This is exactly what happened to me. I was reading 30 Volts and couldn't get what was a previous working light to work. Read here about maybe a 3 way switch causing phantom reading, went over and flipped the other switch on and immediately got 115 120 Volts and all was fine. It was really frustrating when the light didn't originally work as everything has been perfect till I took it apart. – user60913 Oct 4 '16 at 23:32

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