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A friend has asked for my help to replace a wall receptacle that has stopped working. I asked if it was loose-fitting or otherwise physically worn out. She said that plugs fit tightly and it generally seems OK.

Are there faults that could cause a receptacle to fail that I should check for while replacing it? Other than physically wearing out, I've never experienced a receptacle that simply quit working.

The house is old, possibly nearing 100 years. The receptacle likely does not have a modern ground wire to it. It was used for her computer and unlikely ever needed to supply more than a few amps.

  • Are you sure it's the receptacle that failed? It could also be the wire or connections leading up to the receptacle (in my experience, old stab-in-back receptacle connections can come loose without affecting how the outlet feels when you plug things in -- I've had this cause a downstream daisy-chained outlet to stop working while the outlet with the loose stab-in-back connection to feed the other outlet continued working just fine). – statueuphemism Jan 31 '17 at 15:37
  • Easy thing first is to check for blown fuses/breakers, or any GFCIs that may be upstream of this outlet (GFCIs are one way to deal with no ground, though all outlets downstream should technically be marked 'GFCI Protected' and 'No Equipment Ground'). – gregmac Jan 31 '17 at 15:46
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    When working with old wiring, be careful to not manhandle it by moving it around a lot. This is easier said than done but the old insulation will crack when moved. You can wrap the old wires in electrical tape to help with this. Another thing to consider is that if there is no ground, any surge protection is going to be useless at that outlet. – JimmyJames Jan 31 '17 at 17:08
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    In a house that's 100 years old there could be a dozen different wiring problems that might account for this. Pretty much impossible to guess without some diagnostic efforts. – Hot Licks Jan 31 '17 at 21:36
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A GFCI upstream

This outlet may be supplied from a GFCI/RCD outlet upstream, which has tripped or failed. Since you think this circuit doesn't have ground, this would be a good reason to have used a GFCI. People generally use GFCI receptacles, even in odd places, because they are cheaper than GFCI breakers.

Stab connections

A common reason for a socket to fail is the "back stab" connections on the back of the socket. These are holes you jab the wire into, and then "magic springs" hold the wire in. And the socket must cost 50 cents wholesale, which tells you the wizards aren't really making an effort. This is not a quality receptacle, and it will tend to fail there.

Switching to the screw connections helps, and using a more quality $4-tier receptacle also helps. Some of them have screw-and-clamp, where you jab the wires but must use the side screws to clamp the wire, those are fine.

Aluminum wiring

Mainly a problem for homes wired in the 50s and 60s, a reault of having a housing boom at the same time 3/4 of the civilized world is rebuilding from the ashes, which overwhelmed the copper mines. Aluminum wire can be tolerated, but needs special splicing that is beyond the scope of this answer. Ask.

Is it grounded?

It is grounded if there's a continuous grounding path from the receptacle to the panel... and that ground is either wired to the receptacle, or wired to a steel junction box and the receptacle's metal yoke (ears) is bottomed out hard against that metal box. If the yoke bottoms out on plaster or drywall and there's a gap to the metal box, not good enough.

If there is not a good grounding path, then either

  • install a 2-prong receptacle. This is unrealistic, as the tenant will defeat it with cheaters or breaking off ground pins, and you can't allow that.
  • install a GFCI receptacle, or assure that this receptacle is fed from a GFCI receptacle or breaker, rated for personnel protection. Label the receptacle "No Equipment Ground", and "GFCI Protected" if that is not obvious.
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A receptacle is merely a means to connect a device to the power source. It can fail for many reasons.

Short Circuit

If the hot lead directly touches neutral or ground, a short circuit will occur. If the line is protected by a circuit breaker, it will disconnect the outlet and connecting wires from the power source at the main panel and no current will flow. If you have fuses, the fuse from that circuit will blow, also disconnecting the power. If the fuse or circuit breaker failed to work properly (rare), it could result in a fire caused by overheating of the wires.

This type of problem can occur in the body of the receptacle, in the wires in a box, or somewhere along the wire path.

Break in Continuity

If there is a gap in either the hot wire or the neutral wire or its attachments, no current can flow, and the outlet will not work. However, if the break is in the neutral, even though the circuit does not work, there is power in the hot wire and poses a risk if it is touched.

The gap in connection can occur in the the receptacle itself. It can be a break within the body or a movement of the metal leaf that is supposed to contact an inserted plug, but does not. It also can occur in the attachment of the wire to the receptacle itself, in a connection within the box (loose or disconnected) or somewhere along the length of the wire.

The break can also be caused by a circuit breaker, GFCI or AFCI device or fuse tripping based on a detected fault. This can occur because of a short, a high amperage flow, an arc in the circuit, or a ground fault. Reseting the device may restore power, assuming the fault has been cured, but it is important to determine what caused the fault to ensure safety.

Solutions

It is important to test to determine whether there is any power at the outlet itself before starting to fix the problem. This requires a tester and a bit of knowledge about circuits. If you are not familiar with these things, it might be better to call in an electrician or someone with some experience to help.

Cures may involve simply fixing a loose connection or replacing the outlet. But it may require tracing a break or short and solving a more complex circuit problem.

  • If there was a short circuit there would be a blown fuse or a fire. – Hot Licks Jan 31 '17 at 21:37
  • @HotLicks I'll clarify. – bib Jan 31 '17 at 21:38
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Several things come to mind:

  1. Check other receptacles in the house. Are any others not working suddenly? If so this suggests a problem with the line, or a blown fuse/tripped breaker.

  2. If this is the end of the line, then the receptacle or the line leading to it may have been damaged. The line might be related to a rodent infestation as they tend to chew everything.

  3. There may be some kind of fuse in the outlet. Uncommon but possible.

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