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I have two ceiling fans powered by 2 (3 way switches}. The fans stopped working so I checked the voltage across the terminals on each 3 way switch. The voltage goes from 120 to 74VAC in about 5 seconds on my digital meter. I replaced both switches and still have the same problem.

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  • Your reading across fried motors; disconnect the fans and I bet it's fine. I also don't trust digital meters.
    – Mazura
    Commented Aug 17, 2015 at 22:06
  • How are you taking the measurement, where exactly are your probes?
    – Tester101
    Commented Aug 17, 2015 at 22:30
  • FYI, both fans are remote controlled with 2 remotes and are fans only, no lights. Commented Aug 18, 2015 at 3:55
  • Yes, I changed batteries in both remotes. Test probes are on common terminal and traveller terminal Commented Aug 18, 2015 at 5:10

1 Answer 1

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If you're measuring voltage by touching your probes to the terminals on a single 3-way switch, you're not accomplishing much. Your readings will come out as follows.

voltage readings across 3-way terminals

From common to the closed traveler terminal, you'll read 0 volts. This is because common is electrically connected to this terminal, so they're at the same voltage potential.

From common to the open traveler, you'll get some arbitrary value between 0 and line voltage. This is because one of the travelers is floating, and has no reference to ground or the line.

Between the travelers, you'll again get an arbitrary value.

voltage readings across 3-way terminals

From common (or the closed traveler) to the open traveler, will yield a line voltage reading, if the other switch is in the opposite position. This is because the other traveler now has a reference to ground, through the load.

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  • I agree; however, when I flip the switch I'm testing, the terminals read a fluctuating voltage drop from approx 108 to 74 volts in a few seconds. The fans have both been working fine until one day recently, they both died. Seems odd that two fan motors would fry at the same time. Not sure what else to test. I did notice that one of the 3 way switches is in a bank of two other 3 ways and all have the same common wire looped between the three of them. Commented Aug 19, 2015 at 11:53
  • @GaryCarter I'm still confused. If you're measuring across the switch as in the first diagram, the fan (load) will be on. You'll either measure 0 volts, or nonsense. If you're measuring as in the second diagram, the fan (load) will be off. And you'll be measuring 0 volts or line voltage. If your measurement is bouncing from 108 - 74 volts when the switches are open (load off), then you have a problem with the supply, not the load. You either have a bad connection along the ungrounded (hot) conductor, or (more likely) a bad connection along the grounded (neutral) conductor.
    – Tester101
    Commented Aug 19, 2015 at 12:29
  • Where would I look for a bad connection on a grounded neutral? Commented Aug 19, 2015 at 13:43
  • @GaryCarter At any connection along it's length. Check all twist-on wire connectors, screw terminals, etc.. Any where the wire is connected to anything else.
    – Tester101
    Commented Aug 19, 2015 at 13:57
  • Thank you, will start checking today and keep you posted. Commented Aug 19, 2015 at 14:06

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