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Our overhead kitchen lights (florescent fixture) stopped working yesterday. The fixture is controlled by a "3-way switch" setup (separate switches for each entrance into the kitchen). First, I turned off the power to the kitchen light circuit and individually tested the switches for continuity; both seem to work properly. So then I tested the voltage coming into the light fixture (with the ballast disconnected on the hot end). With the switches set such that the light should be on, I read 35V. Huh? So I switched one of the switches off. Power from the ceiling (just a hot and neutral with no ground) was still at 35V. No matter the 4 possible combinations of the switches, the light fixture was always being fed 35V (which I expect isn't enough voltage to fire up the ballast). I then tested between the hot and neutral at one of the two switches. It read 71V. Huh??? again!

This is a strictly residential, single-family house with standard 200A service - no multi-phase supply nonsense. It is a 70 year old house, so some of the wiring (the original wiring) is somewhat nasty. With however my meter is calibrated, wall sockets measure at 125V (at least in the expected range); the bathroom lighting shares the breaker circuit with the kitchen lighting, and a socket in the bathroom light fixture also measures at 125V.

What could be going on to explain this (I mean specifically, not just "bad old wiring")?

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    Obviously you have a bad connection somewhere. Very often a voltmeter will read anywhere from 10 to 80 volts when there is a bad connection.
    – Hot Licks
    Oct 15, 2022 at 23:31
  • Sounds like you might be experiencing phantom voltage. diy.stackexchange.com/questions/136436/…
    – maples
    Oct 16, 2022 at 3:34

2 Answers 2

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OK - it seems that one of the wires feeding one of the switches was almost broken. When I pulled the switch out again to test, it broke completely. Rewired that terminal, and the voltages are all as expected. Lights still didn't work, so bought a new light.

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Verify the voltage out of both switches including the traveler. If the result is 125V the wiring to the light has encountered something to drastically increase it's resistance. What that is will require inspection of the wire.

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  • It is possible they did a split and ran 2 120V (220V between them) circuits with one neutral. If so it appears the neutral is open or failing probably at a splice in a box.
    – Gil
    Oct 16, 2022 at 21:17

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