What's going on with our wiring?
November 14, 2010 8:38 AM   Subscribe

Old house, strange wiring issue. Electrician will be called, but any idea what's going on?

1923 house, purchased a few months ago. Yesterday, our front foyer and outside porch lights suddenly went out. Further investigation revealed a whole circuit is not working (including one living room outlet and all but one of the outlets in the upstairs bedroom). However, nothing on our breaker panel is tripped, and turning off/on every single breaker just to be sure didn't help. Changing the two light bulbs didn't help either.

We'll be calling our electrician 1st thing tomorrow, but any ideas of what could be going on, or anything else we can try? It's an old house with old wiring. Not knob and tube, but much of it is what they call "BX" wiring. 100 amp service, brand new electrical panel installed a few months ago.
posted by misskaz to Home & Garden (8 answers total)
Best answer: One thing that could cause this would be an interrupted circuit. It's not that the circuit is shorting out, but that a wire has been physically disconnected somehow.
posted by spikeleemajortomdickandharryconnickjrmints at 8:48 AM on November 14, 2010

Best answer: A splice has obviously come apart
with a meter you could tell which one and trace it back
if its aluminum wire it tends to get brittle with age at the splices
posted by SatansCabanaboy at 8:49 AM on November 14, 2010

Earlier this year we lost power to half the house (mostly, but not exclusively the front of the house). Nothing in the breaker box had tripped. Later that day the power company fixed the blown transformer that had killed one of the two 120 lines feeding my neighborhood.

If you think this might be the case at your place, unplug any 240 volt appliances and call your power company.
posted by jindc at 9:00 AM on November 14, 2010

Yesterday, our front foyer and outside porch lights suddenly went out.

Could be a rodent chewed the wiring over the outside porch, it's the time of the year when they are moving inside.
posted by ennui.bz at 9:11 AM on November 14, 2010 [1 favorite]

Is there a GFCI anywhere in the circuit? If this has tripped, anything downstream of it will shut off as well.
posted by davey_darling at 9:35 AM on November 14, 2010

Best answer: spikeleemajortomdickandharryconnickjrmints and SatansCabanaboy that you've probably had a splice or junction fail. With BX (or AC = Armoured Cable) it's pretty unlikely that the problem is a rodent.

There is a possibility for a dangerous condition to have been created if the break is on the neutral side. If your panel is labelled you should turn off the breaker feeding that circuit until the electrician comes. If you can't figure out which breaker it is then unplug everything from the affected circuit.

It's also possible the breaker is defective, especially considering your panel is pretty recent. The only way to check this is with a meter after opening your panel. Something you should avoid unless you know what you are doing.

If the break is on the hot side then a proximity voltage tester may allow you to pin point the break. This is only useful if you plan on fixing it yourself though so don't spend the money on the tester (~$15) unless that is your plan.
posted by Mitheral at 11:24 AM on November 14, 2010

Best answer: A splice that's come undone seems like the likely culprit. Probably something near the junction between the old wiring and the new (couple of months old) wiring— the anecdata I've heard is that ancient wiring is usually reasonably reliable until it's disturbed by renovations.

davey_darling's suggestion of a GFCI outlet is a good one to check before hiring an electrician though. Mostly they're found in bathrooms, but it's not unheard of for them to be placed elsewhere as well. Someone might have decided that protecting the porch lights with a GFCI was a good idea since they're exposed to the weather.
posted by hattifattener at 11:45 AM on November 14, 2010

Response by poster: Thanks, guys! Electrician took a look today and found hinky wiring in the foyer light fixture (Old somewhat "crunchy" [his word] wires + previous homeowner DIY fixture install with tape and no wire nuts + fixture box too small so wires are all jammed in there.) $150 plus a recommendation to get a new fixture and we're as good as we can be with our ancient wiring.
posted by misskaz at 11:10 AM on November 18, 2010

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