wiring fault

I plugged a APC UPS system in to a socket in my house and a red light came on that is labeled "wiring fault." Does this mean there is no ground or is it detecting some other problem? Is there a way to trouble shoot and find what the fault is?
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In my experience, the lights on the UPCs are about as useul as the "check engine" light or "service engine now" light in cars. enough to tell you to look at it, but not enough to tell ou what is wrong. And no 'codes" to pull to help diagnosis.
I think there are only two things that can be wrong. First and most commonis reversed polarity at the socket. Neutral on hot side and hot on neutral side. Or in simpler terms white wire on dark brass screw, black wire on bright silver screw. Note that the mix up ca be in a different outlet box than the one where you are connecting the UPS. It could be futher up the daisy chain.
The other error that the UPC could be picking up is an open ground.
I'm not going to give instructiomns on line because I don't want any liability if you do it wrong. If you do already knw your way arund AC branch circuits, both are easy but sometimes tedious tests with a quality digital multmeter and a pair of Mark I eyeballs, and are eually easy but sometimes tedious repairs.
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Jim McLaughlin

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Jim McLaughlin wrote:

I agree with everything you say, Jim. Except:
Why advise his using a "digital" multimeter rather than a good old fashioned analog one?
Haven't we had enough questions here about "phantom" voltage readings confusing non-technical folks? Those misleading readings occur because of the extremely high input impedance of digital multimeters responding to minute AC currents coupled by interwire capacitances. <G>
Jeff
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Jeffry Wisnia
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Bob wrote:

One of the $10 ($15 with GFCI tester) little plug in three light testers you can get most anywhere will identify most common wiring problems just fine. Once you identify the problem either tackle it referencing a DIY home wiring book from the library or have an electrician fix it for you depending on your confidence / skill level.
Pete C.
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Pete C. wrote:

Plug in testers can indicate a bad outlet but won't necessarily indicate a good outlet. They run on very low current and, in particular, can't give a reliable test of the ground wire. I would be more extreme than Jeff and use a lightbulb in a pigtail socket.
bud--
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Bud-- wrote:

It the fault was detected / reported by the APC UPS then the little tester should readily identify it. The UPS isn't generally the most sophisticated electrical tester.
Pete C.
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Bob wrote:

You could try reading the manual ...
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I have this same problem. Just bought a house that was built in the early 50s. Put all of the computer equipment in the only bedroom that had 3-pronged outlets and my UPS wiring fault lite came on. Killed the CB and unscrewed the plug-in and sure enough, the prior owner replaced the the old socket with a new one but did not add a ground wire. Now I am getting ready to replace all of the wiring with new 12-2 w/g wire.
Bob wrote:

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