Strange switch feed line issue

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Old 03-02-10, 06:15 AM
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Strange switch feed line issue

A tenant reported that a light was out in their apartment. I removed the switch and used a home-made test light to check for power to the switch. There wasn’t any. I then went to the basement to track down the feed wire that was leading up into the bedroom. I found it and followed it to the junction box. I tested the feed wire to the junction box to make sure it had power and then reconnected the line. I then went back up to the switch and found that my test light lit up twice, but not again. I also noticed little sparks as I used the test light and rubbed the wires along the exposed switch wires. The circuit breaker does not trip.

Any ideas?

Thanks for your input.
 
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Old 03-02-10, 06:36 AM
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It sounds like you may have fixed the problem but blew the bulb in your homemade test light? You would probably get an arc when rubbing the wires with your light.
 
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Old 03-02-10, 06:54 AM
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I used the test light in another location after I checked the switch. I thought that the exposed portion of the switch feed wires were corroded? so I scraped them and I was still unable to get the test light to light up. I did see the tiny sparks occasionally again though.
 
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Old 03-02-10, 07:16 AM
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If you take the switch out and touch the two wires together can you make the light work? If so replace the switch.
 
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Old 03-02-10, 07:27 AM
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The first step I did was to take the switch out and test if power was reaching the switch. Since I can't get the test light to light up with the wires that feed the switch, I am assuming the problem is not with the switch itself, rather, the lines that feed the switch.

Does that make sense? Thanks.
 
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Old 03-02-10, 07:32 AM
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Originally Posted by treefrog View Post
The first step I did was to take the switch out and test if power was reaching the switch. Since I can't get the test light to light up with the wires that feed the switch, I am assuming the problem is not with the switch itself, rather, the lines that feed the switch.

Does that make sense? Thanks.
Maybe? On a switch loop with no neutral you would need to test to ground and only one wire would be hot with the switch off or removed. Do you have a switch loop? Did you check to a known good ground?
 
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Old 03-02-10, 07:35 AM
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It does make sense so the next step is to make sure the connections at the light and the junction box are good and tight. I usually take them loose and re-connect with new twist on caps. If that doesn't work I would say a new line from the junction to the switch is in order. could be a bad line in the wall.
 
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Old 03-02-10, 09:34 AM
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The bedroom contains two outlets that work even when I disconnected the supposed switch feed wire from the junction box. This isn't surprising because most outlet and switch circuits are separate. I also checked the adjacent room switchs (lights) when I have disconnected the supposedly wire that goes to the problem switch. All those lights still work, so I think this switch wire is dedicated for the problem switch.

I have not tested the ground. The cable is BX so there is a ground wire connected to the metal switch box.

How do I test the ground?

I am trying to avoid running a new wire, but I may just have to. Luckily, it is a first floor.

Thanks for your quick replies.
 
  #9  
Old 03-02-10, 10:16 AM
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What I do, Treefrog is hook my tester to the known hot side of the switch and then to the box.
 
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