Voltage in wires after turning off the wall switch

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Old 08-18-14, 10:53 AM
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Voltage in wires after turning off the wall switch

Hello everybody,

I'd like to know if this is normal. I'm replacing a ceiling lamp. It's a simple box with ground to the box wire, white and black wire.

When the wall switch is on, and circuit breaker on, I have 119V between black and white, 119V between black and ground, 0V between white and ground.

When the wall switch is off, there is still voltage at the wires as follows: black to ground 119V, black to white 93V, ground to white 5V.

If I turn off the circuit breaker, all goes to 0V.

Is this normal? Could there be a short somewhere?
 
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Old 08-18-14, 10:59 AM
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Welcome to the forums! How many cables do you have in the ceiling box? On the switch, what are the colors on the switch. If you have 2 or more cables in the ceiling box, and a black and white wire pair on the switch, then the power comes in the ceiling box, and you have a switch loop to the switch. Power will always be present in the ceiling box if that is the case. That is why just turning off a switch is not always safe to allow work on a ceiling box. The breaker should be turned off.
 

Last edited by ray2047; 08-18-14 at 11:14 AM. Reason: Typo
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Old 08-18-14, 12:34 PM
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Thanks. At the ceiling box there are two wires. The ceiling box was connected in the past with three wall switches, of which one was removed and two are still functional. At one of the two wall switches, I have indeed three wires, a red on one side and a black and one red on the other side. All three wires are connected. It's an on/off switch plus a variation knob.

I'm surprised there is still voltage between the black and white wire at the ceiling box (with the switch off), yet the lights turn off? I grabbed with my hands the black and white wire and felt nothing, yet when I also grabbed the ground I got a nice shake.

I was wondering about having a short because a wall switch was removed (the wires are in the wall now) and I don't know if those wires have been properly isolated.
 
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Old 08-18-14, 01:05 PM
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Were you using a non-contact detector?
 
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Old 08-18-14, 02:08 PM
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I use a 200V-500V DC multimeter
 
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Old 08-18-14, 03:20 PM
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Multimeter needs to be set to AC. Was it analog or digital.
I was wondering about having a short because a wall switch was removed (the wires are in the wall now) and I don't know if those wires have been properly isolated.
A safety and code violation that needs to be fixed by putting them in a permanently assessable box.
At one of the two wall switches, I have indeed three wires, a red on one side and a black and one red on the other side. All three wires are connected. It's an on/off switch plus a variation knob.
Do you mean a dimmer? What about the other switch?
 
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Old 08-18-14, 05:14 PM
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I'm sorry, I meant AC - alternating. It is a digital multimeter.

Yes, the switch with three wires has both a dimmer and an on/off switch, like the third one in the picture. The other active switch is only on/off. The one that has been removed, I don't remember what it was, more probably also only on/off.
 
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Old 08-18-14, 05:28 PM
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Digital meters can give false readings do to induced voltages or bad batteries. Best to double check with an analog multimeter. Not saying that is it just an elimination that should probably be done.
Yes, the switch with three wires has both a dimmer and an on/off switch, like the third one in the picture. The other active switch is only on/off.
Are you saying it is not a 3-way switch. A 3-way switch has no on/off. It should be a 3-way switch.
 
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