Totally dead light switch - need some help

James_TomJuly 14, 2012

One day, I go into the guest bath and the lights don't come on. I remove the light switch, turn the power back on, and there's no voltage in the wires going into the switch. There's absolutely no electricity going into that light switch.

There's another receptacle in the bathroom, and that works fine. It's on the same circuit as the light switch.

Before I call the electrician, can someone provide some more basic troubleshooting I can do?

Thanks...

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mike_kaiser_gw

First place I'd start would be looking for tripped GFCI. Depending on how old your house is, that GFCI could be anywhere. I had a house where the GFCI that controlled the bathroom was in the garage.

    Bookmark   July 15, 2012 at 9:35AM
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James_Tom

Thanks, I checked all the GFI outlets that I'm aware of and I also checked every outlet in the house. They were all working.

I read on a website to check continuity between ground and neutral. When I did that, I found that they were connected, which the website says means that it is not likely the GFI issue.

Is this starting to look like an open circuit? Any other recommendations?

    Bookmark   July 15, 2012 at 7:50PM
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yosemitebill

I'm not trying to be arrogant or disrespectful, but if I went into my bathroom and the light did not turn on, the first thing I would do is replace the light bulb and not pull the light switch out.

Was there some reason to go there first? How are you measuring the voltage at the switch? It could be a switch loop where measurements would need a known neutral or ground for an accurate measurement of voltage present.

I'm sure with a little more info, someone could give you some more advice to go on - look for things such as faulty back-stab connections and such.

    Bookmark   July 15, 2012 at 9:47PM
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James_Tom

Yes I agree, changing the light bulb would be my first suggestion as well. But it's not the bulb because the lighting unit has 4 bulbs, and they can't all fail at the same time.

I measured the voltage using a digital multi-meter. I also used the NVM mode on the digital multimeter (makes a buzz when AC is present I guess) and the area around the switch was silent.

In NVM mode, I moved the multi-meter a little to the left and I was able to pick up a signal about 3 - 4 inches to the left of the switch. Not sure if those wires are meant to go into that switch or meant to go somewhere else.

Anyway, I hope that info can help someone help me to figure out the issue. I'm an Electrical Engineer but home wiring is not my thing.

    Bookmark   July 15, 2012 at 11:31PM
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elltwo

Is the switch the only device in the switch box?
If so, how many strands of wire are in there?
If there are just two and they are both connected to the switch then the problem may be at a splice in a box or fixture before the switch.

    Bookmark   July 16, 2012 at 6:32AM
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hendricus

There's another receptacle in the bathroom, and that works fine. It's on the same circuit as the light switch

Start checking at the last known working outlet, could be that there is a feed through that broke connection.

    Bookmark   July 16, 2012 at 9:27AM
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James_Tom

Elltwo,

There are 2 switches in the box - one for the lights and one for the fan.

There are 3 black wires, 3 white wires and 2 ground wires. Each pair of black and white wires are coming into the box separately.

I took all the wires out, so I forgot how they were wired up, but why 3 pairs of wires?

    Bookmark   July 16, 2012 at 11:09PM
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elltwo

Three pairs of wires would me think that one is the feed in (the line, from the panel, but maybe with a box or splice in between electrically speaking), and two are feed outs (the loads). A continuity tester is useful in identifying the loads.

If this is so then all of the whites should be spliced together, and grounding should be accomplished as well as possible.

If both switches are single pole and operated before the problem then each of the switches should go to one of the blacks.

The remaining black (feed in) should be made into a pigtail (a wye) " Y > with each end of the Y attached to the screw on the switch that you did not use for the feed out. This assumes that both switches have just two screws not counting any ground screw.

If the fan used to work and the wiring is the way I just described then I think you probably had a loose splice in the switchbox, but I wonder why you got no signal in the region of the switch with your tester. You said you picked it up 3-4 inches to the left.

There some wiring schemes that could defy this, but while you have the wires separated check if any other outlets are de-energized.

    Bookmark   July 17, 2012 at 7:36AM
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