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.
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.
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.
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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