Ceiling light, switch wired to neutral. Measuring ~V with switch on and off

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Old 02-11-12, 07:01 PM
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Lightbulb Ceiling light, switch wired to neutral. Measuring ~V with switch on and off

Hi All,

I am replacing a light fixture with a ceiling fan. When I measure the hot black wire with respect to neutral with multimeter I am reading ~120V whether the switch is on or off. I spoke to an electrician who insured me that this is because the switch is actually switching the neutral and NOT the hot wire. This makes sense to me.

What I am confused about is this: If I am measuring ~120VAC with the switch open or closed (between the hot and neutral wires with the fixture not hooked up), then why when I hook the light up does it still turn on and off with the switch?

I would think that if I can measure voltage off of the bare wires regardless of the switch position then the light should be on regardless of the switch position but this is not the case. When I have the fixture hooked up it does turn off when the switch is off!!!
 
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Old 02-11-12, 09:22 PM
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When I measure the hot black wire with respect to neutral with multimeter I am reading ~120V whether the switch is on or off. I spoke to an electrician who insured me that this is because the switch is actually switching the neutral and NOT the hot wire. This makes sense to me.
Well it doesn't make sense to me. Now if you were measuring hot to ground then yes but that would mean you had a major code violation.

I would think that if I can measure voltage off of the bare wires regardless of the switch position then the light should be on regardless of the switch position but this is not the case.
Bare wires are not neutral they are ground. So which wires are you measuring to, neutral or ground.
 
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Old 02-15-12, 02:47 PM
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It was not unusual for wiring done before 1940 to have a switch in the neutral rather than in the hot line. You can leave it that way if you replace the light fixture only. If you modify the wiring you must correct it with the neutral continuous to the light fixture, and only the hot wire connected to the switch.

Is the switch handle "illuminated" with a small incandescent lamp, to light up when the main light is off? This will cause 120 volts to show through between hot and neutral with the switch in either position and the main light removed, when you use a voltmeter. WIth the main light wired up, hot to neutral across the light will register approximately zero volts with the switch "off".
 
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