Weird voltage on receptacle

[Ryan902]

Hey there, I was helping a friend out who has a receptacle she claims "wasn't working". I pulled the plug out and started taking readings with my multimeter, and noticed between the hot and neutral conductor that I was getting 78 volts. Between hot and ground, and neutral and ground, both read zero volts (nominal). I found this very odd and at first assumed a lost neutral, not in not so sure. The wiring was very old and I wasn't sure if there was a ground fault on the box, and couldn't see any evidence of box bond but didn't have a closeby bonded box to compare voltage potential. I didn't have much time, so left it as is and shut the breaker off in the mean time.

I'm going to spend more time looking at it but was just wondering if any gurus see a pattern here?

Thanks for any help.

Sent from my SM-N981W using Tapatalk

 

[LarryFine]

Not a pattern, but some troubleshooting advice.

A high-impedance volt-meter is a poor choice for a tester troubleshooting; I recommend a solenoid tester, or at least plug a night-light or other load in the receptacle while testing.

Also, plug a 3-wire extension cord into a known-properly-wired receptacle to use the female end as references against which to test for proper hot- and grounded-conductor continuity.

Lastly, make sure it's not a switched receptacle. It's rare for only one GP-circuit receptacle to stop working.

 

[Another C10]

noticed between the hot and neutral conductor that I was getting 78 volts. Between hot and ground, and neutral and ground, both read zero volts

could be a poor connection of the upstream hot and also an open ground connection. I've noticed many times voltages like that are many times from arced connection points either through wire nuts or devices. Just a thought.

 

[Sarge56]

Ryan, did you determine the problem? Larry makes a good point about using a solenoid tester (Wiggy). I have had apparent voltage with a digital multimeter that disappears with a Wiggy. Clearly you have an open ground at the receptacle. Probably an ungrounded 2-wire system. It could be as serious as an open neutral at the service, but that would be very apparent. A bad connection probably would not reduce your digital reading to 78. I am guessing your original thought about the neutral is spot on.

 

[Sarge56]

Or, and this is very possible, 2 circuits with a shared neutral and a lost neutral at some point within the circuit. Voltage would fluctuate according to load.