Trying to find source of voltage on ground wire?

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Old 04-08-14, 11:20 AM
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Trying to find source of voltage on ground wire?

I had a bedroom ceiling fan go out. It's on a circuit that feeds outlets and ceiling lights in two bedrooms + 1/2 bath in my 60's ranch using 12 gauge with ground wire.

In some legs of the circuit I found 17V between black and white wires & 123V between black and ground wire. Outlets on other legs of the circuit show proper voltages.

1) Voltage on the ground wire instead of white wire means there is a short or bad connection somewhere in the circuit, right?
 
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Old 04-08-14, 12:41 PM
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In some legs of the circuit I found 17V between black and white wires & 123V between black and ground wire. Outlets on other legs of the circuit show proper voltages.

1) Voltage on the ground wire instead of white wire means there is a short or bad connection somewhere in the circuit, right?
It doesn't sound like you have any voltage on the grounding conductors (the ground wires) in that circuit. It sounds like you have an open or loose connection in the grounded conductor (the neutral wire).

The 120V live potential in your system is on the ungrounded conductors (the "hot" wires). That potential should always be present hot-to-ground and hot-to-neutral. Since it isn't present hot-to-neutral, you need to turn the power for that circuit off at the panel and start tracing the wiring from the ceiling box where you discovered the problem back toward your panel. See Troubleshooting a dead receptacle or light,....

Check all connections as you go, but pay special attention to the ones on the neutral wires. In particular, take all splices apart and make sure all of the conductors inside are in good condition and that the splice is tightly twisted. If the wire nut you took off doesn't look nice and clean inside, or doesn't have a steel coil in it, replace it with a new one that does after you re-make the splice.

This is on the hot side and doesn't enter into the problem at hand, but I would also use this opportunity to change any back-stabbed connections you find to the screw terminals.
 
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Old 04-08-14, 01:12 PM
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Thanks. I realized I worded the problem poorly.

During troubleshooting something puzzled me after I disconnected the wires in the central junction box so I could test each leg of the circuit.

If I touched the hot wire on the feed from the panel to the hot or neutral wire on one of the disconnected legs I was getting voltages (48V on one leg and 67V on the other). Is that normal?
 
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Old 04-08-14, 01:36 PM
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It's called phantom voltage, and is common with digital meters. You would be better off with an inexpensive analog meter for better troubleshooting readings
 
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Old 04-08-14, 01:44 PM
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A cheap analog multimeter rejects phantom voltage better then a cheap digital so we usually recommend a $8-$15 analog rather then a digital multimeter.
 
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Old 04-08-14, 02:40 PM
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Fixed: I redid the connections in the junction boxes and voltages are showing correct now.
 
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Old 04-08-14, 03:04 PM
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Glad you got it, and thanks for letting us know what you did.
 
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