HELP: Electrical circuit woes ...

All, I'm helping a friend diagnose a circuit that just stopped working. After some diagnosis, we've come up with the following:
1) The outlet that is not working has 20VAC between the white and black wires (?) and 120VAC between the black and ground wires. Thus, I can power the two-prong lamp off black and ground, but not by plugging it in (between black and white).
2) I have not had time to determine what is between the circuit breaker and this outlet, but I am suspecting there may be a bad GFCI somewhere due to the voltage difference between white and ground wires. We did a quick check of the GFCI (by pressing test and reset) and they *appear* to work fine, but I am still skeptical.
Any suggestions would be appreciated.
Take care, Chris
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You have an open neutral. Look for loose neutral connections in outlets adjacent to the dead outlet, especially back stabbed connections

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M100C wrote:

Your tests indicate that the White wire is open-circuit *somewhere*. Maybe in a GFI (but not too likely since the Blk is still solid).
It could be a bad splice in god-knows which junction box, or even at the panel Neutral bar.
Or, if the recept you are at is tapped off another recept, the screw/stab connection at the tap point may be open.
This kind of thing can be nightmarish to track down if you don't know the exact path the circuit run takes.
Jim
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M100C wrote:

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M100C wrote:

I agree with all 3 previous posts and would add only that the 20 volts is not real. The open white wire has capacitance to the hot wire which produces a voltage on a high resistance, probably digital, meter.
bud--
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I agree with the four previous posters that you have an open neutral. To find it, first locate the circult breaker at the panel that shuts off this problem outlet. Then test all the outlets and switches/lights in the room and mark all that are also turned off by this breaker.
Try to draw the shortest line that connects all the outlets and switches/lights that are off. Please draw the line in your mind, not on the wall :) This line hopefully represents the order of how the outlets and switches are wired inside the wall.
There are two possibilties:
The outlet is at the endpoint of the line. The outlet is not at the endpoint of the line.
If the outlet is at the endpoint of the line, then the open neutral happens at either the problem outlet, or the upstream one.
If the outlet is not at the endpoint of the line (and is the only outlet with problem), then the open neutral can only happen at the outlet.
Therefore, to find the loose neutral wire, first examine the problem outlet.
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