I have a branch with few outlets and ligths on it, and one outlet developed a problem overnight, in the sense that whatever was plugged into it was energized last night, but was not in the morning. The breaker did not trip.

While troubleshooting I found that the voltage between hot and neutral on that outlet is about 90V, while the voltage between hot and ground is 110V, as expected. I opened up a couple of other outlets, one on the same branch, another on a different branch, and both show 110V between hot and neutral.

I replaced the problematic outlet but it did not help.

What would be my next steps in troubleshooting/fixing it, apart from calling a professional?

  • 2
    You probably have a loose connection on the outlet before the problem one. I would guess the neutral is the loose one but tighten all the others to the correct torque values.
    – crip659
    Commented Jan 21 at 14:56

2 Answers 2


Work backwards through all other receptacles and other junction boxes (e.g., sometimes in switch boxes or light fixture boxes, and sometimes boxes that are only for connecting things) towards the circuit breaker. There is most likely a loose connection somewhere. Any type of connection can be loose, or just so little metal connecting that it functions like a loose connection.

  • Backstabs - These are the worst. If you find any, move them to screw terminals.
  • Screw terminals - Should loop around clockwise - otherwise tightening pushes the wire out. Should see very little copper not under the screws. Should not see any insulation under the screws.
  • Wire nuts - Do a pull test - if any wire comes out then redo the connection (replacing the wire nut is preferred, but sometimes they can be reused successfully). If a wire nut is loose - you can twist it without the wires turning with it - then redo the connection. If a wire nut is cracked, replace it. If any copper is showing on the wires (except for ground wires, of course), redo the connection.
  • Freshly bought receptacle tester confirmed "open neutral". Now I'll just have to find where...
    – mustaccio
    Commented Jan 21 at 19:32
  • A receptacle tester doesn't truly "know" open neutral. The "open neutral" light sequence means "there is sufficient voltage between hot and ground to light up one light" + "there is insufficient voltage between hot and neutral to light up that light" + "there is insufficient voltage between neutral and ground to light up that light". Which you basically already knew from "90V between hot and neutral". Commented Jan 21 at 19:37

Just for the closure, it was indeed a loose neutral in a wire nut in one of the junction boxes on the way to the problematic receptacle. Replaced nuts with WAGOs and all is well now.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.