Outlet Mystery

Hello all,

I'm a new poster so hopefully I provide enough information for the forum readers.

We have a house that was built in the middle part of the last century and has some wiring "quirks". All of the outlets in the house work fine except for the one in the bathroom where we aren't able to hook up a GFCI. The wiring coming into the outlet box is Romex 12/3 and here's what I find. (Also, I'm guessing that some of the voltages that I'm seeing are from my digital multimeter)

Neutral to Ground - 16V
Hot to Ground - 16V

Neutral to Hot - 0V

Neutral to outlet box - 124V
Hot to outlet box - 124V

Prior to hooking up the GFCI I tested across the hot and neutral and found 124V so I figured that it was good to go. After hooking it up, I get the 0V that you see above in my results.

All of the other outlets and fixtures on the circuit work perfectly.

This problem has so far defeated me, my father-in-law and friends of the family. We've all done electrical work before but are by no means experts.

If you need more information from me, please let me know.

Thanks in advance.

-Jim

 

The 16v readings are most likely ghost readings, a anomaly of using a digital meter. The 124v from hot and neutral to the box seems odd. A few questions:
- Is the ground wire connected to the metal box?
- You mentioned 12/3. Do you mean 12/2 + ground (black, white, bare), or actually 12/3 plus ground (black/white/red/bare).

The best tester though is a $6 neon tester (or many like it).

 

It sounds to me like a hot wire has come in contact with the metal box.
It also sounds like you have 12/2 with ground, and the ground in the cable is not truly grounded.
Check black wires for any nicks or slices in insulation. If you can't find any damaged wires in that box, trace it backwards to the previous box (source) and check that also.

While you're at it, check all neutral connections, disassemble any neutral bundles and reassemble. Any backstabbed devices need to be side wired.

 

You are correct, I did mean 12/2 wire.

The ground wire is not connected to the box but rather comes up via the 12/2 cable. Where that cable actually comes from is a mystery that only the house knows at this point.

My tester is just a run-of-the-mill $10 Craftsman multimeter.

 

The cable looks okay, but I'm wondering about the neutral in the box itself. It seems to have an awful lot of electrical tape attached to it so I'm wondering if that wire is broken inside that "patch".

With regard to the GFCI, I like to wire to the side terminals on outlets as I really just don't like those back stab options for some reason. The side terminals always feel more secure.

I'm going to try to figure out where this outlet is connected to. There is an outlet on the same wall in the room next door so I'm guessing that's where it's coming from.

 

GFCI receptacles don't have back stabs. GFCI receptacles are usually back wire devices, but the wires are secured by tightening the screws which tighten pressure plates securing the wires. It's a very secure and solid connection.